Chrysler Voyager 2000 GS Instruction

NS EMISSION CONTROL SYSTEMS 25 - 1

EMISSION CONTROL SYSTEMS

TABLE OF CONTENTS

page page

ON-BOARD DIAGNOSTICS ................... 1

EVAPORATIVE EMISSION CONTROLS ......... 22

ON-BOARD DIAGNOSTICS

TABLE OF CONTENTS

page page

DESCRIPTION AND OPERATION

SYSTEM DESCRIPTION ....................1

MALFUNCTION INDICATOR LAMP (MIL)........2

DRB III STATE DISPLAY TEST MODE ..........2

DRB III CIRCUIT ACTUATION TEST MODE ......2

DIAGNOSTIC TROUBLE CODES ..............2

DIAGNOSTIC TROUBLE CODE

DESCRIPTIONS .........................3

DESCRIPTION AND OPERATION

SYSTEM DESCRIPTION

DESCRIPTION

OBD II requires that vehicles falling under OBD II

guidelines utilize the following system monitors:

• Comprehensive Component Monitor (inputs/out­puts for powertrain management that affect emis­sions, but do not have a specific major monitor)

• Fuel Control Monitor (fuel compensation
required to maintain stoichiometric ratio rich/lean)

• Misfire Monitor (change in crankshaft speed)

• Oxygen Sensor Heater Monitor (response and

performance of oxygen sensors)

• Catalyst Monitor (Performance and efficiency of
catalyst)

• Evaporative Emissions Monitor (performance of
and leaks from EVAP system)

• Exhaust Gas Recirculation Monitor (flow perfor­mance of EGR system)

The software was rewritten to enable the PCM to
carry out the responsibilities to meet these required
guidelines. The PCM now contains a Task Manager.

EXHAUST GAS RECIRCULATION (EGR)

SYSTEM............................... 27

MONITORED SYSTEMS....................12

TRIP DEFINITION ........................16

MONITORED COMPONENT.................16

NON-MONITORED CIRCUITS ...............20

HIGH AND LOW LIMITS....................21

SPECIFICATIONS

LOAD VALUE............................21

OPERATION

The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a
problem with a monitored circuit often enough to
indicate an actual problem, it stores a Diagnostic
Trouble Code (DTC) in the PCM’s memory. If the
code applies to a non-emissions related component or
system, and the problem is repaired or ceases to
exist, the PCM cancels the code after 40 warmup
cycles. Diagnostic trouble codes that affect vehicle
emissions illuminate the Malfunction Indicator Lamp
(MIL). Refer to Malfunction Indicator Lamp in this
section.

Certain criteria must be met before the PCM
stores a DTC in memory. The criteria may be a spe­cific range of engine RPM, engine temperature,
and/or input voltage to the PCM.

The PCM might not store a DTC for a monitored
circuit even though a malfunction has occurred. This
may happen because one of the DTC criteria for the
circuit has not been met. For example, assume the
diagnostic trouble code criteria requires the PCM to
monitor the circuit only when the engine operates
between 750 and 2000 RPM. Suppose the sensor’s
output circuit shorts to ground when engine operates
above 2400 RPM (resulting in 0 volt input to the

25 - 2 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

PCM). Because the condition happens at an engine
speed above the maximum threshold (2000 rpm), the
PCM will not store a DTC.

There are several operating conditions for which
the PCM monitors and sets DTC’s. Refer to Moni­tored Systems, Components, and Non-Monitored Cir­cuits in this section.

NOTE: Various diagnostic procedures may actually
cause a diagnostic monitor to set a DTC. For
instance, pulling a spark plug wire to perform a
spark test may set the misfire code. When a repair
is completed and verified, use the DRB III scan tool
to erase all DTC’s and extinguish the MIL.

Technicians can display stored DTC’s by using the
DRB III scan tool. Refer to Diagnostic Trouble Codes
in this section. For DTC information, refer to charts
in this section.

Limp-In mode or identified a failed emission compo­nent or system. The MIL remains on until the DTC
is erased. Refer to the Diagnostic Trouble Code
charts in this group for emission related codes.

Also, the MIL either flashes or illuminates contin­uously when the PCM detects active engine misfire.
Refer to Misfire Monitoring in this section.

Additionally, the PCM may reset (turn off) the MIL
when one of the following occur:

• PCM does not detect the malfunction for 3 con­secutive trips (except misfire and fuel system moni­tors).

• PCM does not detect a malfunction while per­forming three successive engine misfire or fuel sys­tem tests. The PCM performs these tests while the
engine is operating within 6 375 RPM of and within
10 % of the load of the operating condition at which
the malfunction was first detected.

DRB III STATE DISPLAY TEST MODE

OPERATION

The switch inputs to the Powertrain Control Mod­ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. From
the state display screen, access either State Display
Inputs and Outputs or State Display Sensors.

Fig. 1 Data Link (Diagnostic) Connector

1 – DIAGNOSTIC CONNECTOR

MALFUNCTION INDICATOR LAMP (MIL)

DESCRIPTION

The data link connector is located at the lower
edge of the instrument panel near the steering col­umn.

OPERATION

As a functional test, the Malfunction Indicator
Lamp (MIL) illuminates at key-on before engine
cranking. Whenever the Powertrain Control Module
(PCM) sets a Diagnostic Trouble Code (DTC) that
affects vehicle emissions, it illuminates the MIL. If a
problem is detected, the PCM sends a message over
the CCD Bus to the instrument cluster to illuminate
the lamp. The PCM illuminates the MIL only for
DTC’s that affect vehicle emissions. The MIL stays
on continuously when the PCM has entered a

DRB III CIRCUIT ACTUATION TEST MODE

OPERATION

The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor­rectly.

DIAGNOSTIC TROUBLE CODES

DESCRIPTION

A Diagnostic Trouble Code (DTC) indicates the
PCM has recognized an abnormal condition in the
system.

NS EMISSION CONTROL SYSTEMS 25 - 3

DESCRIPTION AND OPERATION (Continued)

Remember that DTC’s are the results of a sys­tem or circuit failure, but do not directly iden­tify the failed component or components.

NOTE: For a list of DTC’s, refer to the charts in this
section.

OPERATION

BULB CHECK

Each time the ignition key is turned to the ON
position, the malfunction indicator (check engine)
lamp on the instrument panel should illuminate for
approximately 2 seconds then go out. This is done for
a bulb check.

OBTAINING DTC’S USING DRB SCAN TOOL

(1) Connect the DRB scan tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.

(2) Turn the ignition switch on and access the
“Read Fault” screen.

(3) Record all the DTC’s and “freeze frame” infor­mation shown on the DRB scan tool.

(4) To erase DTC’s, use the “Erase Trouble Code”
data screen on the DRB scan tool. Do not erase any

DTC’s until problems have been investigated
and repairs have been performed.

DIAGNOSTIC TROUBLE CODE DESCRIPTIONS

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

GENERIC

SCAN TOOL

CODE

P0106 (M) Barometric Pressure Out of Range MAP sensor input voltage out of an acceptable range

P0107 (M) Map Sensor Voltage Too Low MAP sensor input below minimum acceptable voltage.
P0108 (M) Map Sensor Voltage Too High MAP sensor input above maximum acceptable voltage.
P0112 (M) Intake Air Temp Sensor Voltage Low Intake air (charge) temperature sensor input below the

P0113 (M) Intake Air Temp Sensor Voltage High Intake air (charge) temperature sensor input above the

P0116 A rationatilty error has been detected in the coolant temp

P0117 (M) ECT Sensor Voltage Too Low Engine coolant temperature sensor input below the

P0118 (M) ECT Sensor Voltage Too High Engine coolant temperature sensor input above the

P0121 (M) TPS Voltage Does Not Agree With

P0122 (M) Throttle Position Sensor Voltage Low Throttle position sensor input below the acceptable

P0123 (M) Throttle Position Sensor Voltage

P0125 (M) Closed Loop Temp Not Reached Time to enter Closed Loop Operation (Fuel Control) is

P0130 1/1 O2 Sensor Heater Relay Circuit An open or shorted condition detected in the ASD or CNG

P0131 (M) 1/1 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal

DRB SCAN TOOL DISPLAY DESCRIPTION OF DIAGNOSTIC TROUBLE CODE

detected during reading of barometric pressure at key-on.

minimum acceptable voltage.

maximum acceptable voltage.

sensor.

minimum acceptable voltage.

maximum acceptable voltage.

TPS signal does not correlate to MAP sensor signal.

MAP

voltage range.

Throttle position sensor input above the maximum

High

acceptable voltage.

excessive.

shutoff relay control ckt.

operating range.

25 - 4 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P0132 (M) 1/1 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal

operating range.

P0133 (M) 1/1 O2 Sensor Slow Response Oxygen sensor response slower than minimum required

switching frequency.

P0134 (M) 1/1 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen

sensor input.

P0135 (M) 1/1 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.

P0136 1/2 O2 Sensor Heater Relay Circuit An open or shorted condition detected in the ASD or CNG

shutoff relay control ckt.

P0137 (M) 1/2 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal

operating range.

P0138 (M) 1/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal

operating range.
P0139 (M) 1/2 O2 Sensor Slow Response Oxygen sensor response not as expected.
P0140 (M) 1/2 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen

sensor.

P0141 (M) 1/2 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.

P0143 1/3 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal

operating range.

P0144 1/3 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal

operating range.

P0145 1/3 O2 Sensor Slow Response Oxygen sensor response slower than minimum required

switching frequency.

P0146 1/3 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen

sensor.

P0147 1/3 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.

P0151 (M) 2/1 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal

operating range.
P0152 (M) 2/1 O2 Sensor Shorted To Voltage Oxygen sensor input voltage sustained above normal

operating range.
P0153 (M) 2/1 O2 Sensor Slow Response Oxygen sensor response slower than minimum required

switching frequency.

P0154 (M) 2/1 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen

sensor.
P0155 (M) 2/1 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.
P0157 (M) 2/2 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal

operating range.

P0158 (M) 2/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal

operating range.

P0159 2/2 O2 Sensor Slow Response Oxygen sensor response slower than minimum required

switching frequency.

P0160 (M) 2/2 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen

sensor.
P0161 (M) 2/2 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.

NS EMISSION CONTROL SYSTEMS 25 - 5

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P0165 Starter Relay Control Circuit An open or shorted condition detected in the starter relay

control circuit.

P0171 (M) 1/1 Fuel System Lean A lean air/fuel mixture has been indicated by an

abnormally rich correction factor.

P0172 (M) 1/1 Fuel System Rich A rich air/fuel mixture has been indicated by an

abnormally lean correction factor.

P0174 (M) 2/1 Fuel System Lean A lean air/fuel mixture has been indicated by an

abnormally rich correction factor.

P0175 (M) 2/1 Fuel System Rich A rich air/fuel mixture has been indicated by an

abnormally lean correction factor.

P0178 Water in Fuel Sensor Voltage Too

Low

P0179 Flex Fuel Sensor Volts Too High Flex fuel sensor input above maximum acceptable

P0182 CNG Temp Sensor Voltage Too Low Compressed natural gas temperature sensor voltage

P0183 CNG Temp Sensor Voltage Too High Compressed natural gas temperature sensor voltage

P0201 (M) Injector #1 Control Circuit An open or shorted condition detected in control circuit for

P0202 (M) Injector #2 Control Circuit An open or shorted condition detected in control circuit for

P0203 (M) Injector #3 Control Circuit An open or shorted condition detected in control circuit for

P0204 (M) Injector #4 Control Circuit Injector #4 or INJ 4 injector bank output driver stage does

P0205 (M) Injector #5 Control Circuit Injector #5 output driver stage does not respond properly

P0206 (M) Injector #6 Control Circuit Injector #6 output driver stage does not respond properly

P0207 Injector #7 Control Circuit Injector #7 output driver stage does not respond properly

P0208 Injector #8 Control Circuit Injector #8 output driver stage does not respond properly

P0209 Injector #9 Control Circuit Injector #9 output driver stage does not respond properly

P0210 Injector #10 Control Circuit Injector #10 output driver stage does not respond properly

P0300 (M) Multiple Cylinder Mis-fire Misfire detected in multiple cylinders.
P0301 (M) CYLINDER #1 MISFIRE Misfire detected in cylinder #1.
P0302 (M) CYLINDER #2 MISFIRE Misfire detected in cylinder #2.
P0303 (M) CYLINDER #3 MISFIRE Misfire detected in cylinder #3.
P0304 (M) CYLINDER #4 MISFIRE Misfire detected in cylinder #4.
P0305 (M) CYLINDER #5 MISFIRE Misfire detected in cylinder #5.
P0306 (M) CYLINDER #6 MISFIRE Misfire detected in cylinder #6.

Flex fuel sensor input below minimum acceptable voltage.

voltage.

below acceptable voltage.

above acceptable voltage.

injector #1 or the INJ 1 injector bank.

injector #2 or the INJ 2 injector bank.

injector #3 or the INJ 3 injector bank.

not respond properly to the control signal.

to the control signal.

to the control signal.

to the control signal.

to the control signal.

to the control signal.

to the control signal.

25 - 6 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P0307 (M) CYLINDER #7 MISFIRE Misfire detected in cylinder #7
P0308 (M) CYLINDER #8 MISFIRE Misfire detected in cylinder #8.
P0309 (M) CYLINDER #9 MISFIRE Misfire detected in cylinder #9.
P0310 (M) CYLINDER #10 MISFIRE Misfire detected in cylinder #10.

P0320 No Crank Referance Signal at PCM No reference signal (crankshaft position sensor) detected

during engine cranking.

P0325 Knock Sensor #1 Circuit Knock sensor (#1) signal above or below minimum

acceptable threshold voltage at particular engine speeds.

P0330 Knock Sensor #2 Circuit Knock sensor (#2) signal above or below minimum

acceptable threshold voltage at particular engine speeds.

P0340 (M) No Cam Signal At PCM No fuel sync

P0350 Ignition Coil Draws Too Much

Current

P0351 (M) Ignition Coil # 1 Primary Circuit Peak primary circuit current not achieved with maximum

P0352 (M) Ignition Coil # 2 Primary Circuit Peak primary circuit current not achieved with maximum

P0353 (M) Ignition Coil # 3 Primary Circuit Peak primary circuit current not achieved with maximum

P0354 (M) Ignition Coil # 4 Primary Circuit Peak primary circuit current not achieved with maximum

P0355 (M) Ignition Coil # 5 Primary Circuit Peak primary circuit current not achieved with maximum

P0356 (M) Ignition Coil # 6 Primary Circuit Peak primary circuit current not achieved with maximum

P0357 Ignition Coil # 7 Primary Circuit Peak primary circuit current not achieved with maximum

P0358 Ignition Coil # 8 Primary Circuit Peak primary circuit current not achieved with maximum

P0401 (M) EGR System Failure Required change in air/fuel ration not detected during

P0403 (M) EGR Solenoid Circuit An open or shorted condition detected in the EGR

P0404 (M) EGR Position Sensor Rationality EGR position sensor signal does not correlate to EGR

P0405 (M) EGR Position Sensor Volts Too Low EGR position sensor input below the acceptable voltage

P0406 (M) EGR Position Sensor Volts Too High EGR position sensor input above the acceptable voltage

P0412 Secondary Air Solenoid Circuit An open or shorted condition detected in the secondary

P0420 (M) 1/1 Catalytic Converter Efficiency Catalyst 1/1 efficiency below required level.
P0432 (M) 1/2 Catalytic Converter Efficiency Catalyst 2/1 efficiency below required level.
P0441 (M) Evap Purge Flow Monitor Insufficient or excessive vapor flow detected during

A coil (1-5) is drawing too much current.

dwell time.

dwell time.

dwell time.

dwell time (High Impedance).

dwell time (High Impedance).

dwell time (high impedance).

dwell time (high impedance).

dwell time (high impedance).

diagnostic test.

solenoid control circuit.

duty cycle.

range.

range.

air (air switching/aspirator) solenoid control circuit.

evaporative emission system operation.

NS EMISSION CONTROL SYSTEMS 25 - 7

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P0442 (M) Evap Leak Monitor Medium Leak

Detected

P0443 (M) Evap Purge Solenoid Circuit An open or shorted condition detected in the EVAP purge

P0455 (M) Evap Leak Monitor Large Leak

Detected

P0456 Evap Leak Monitor Small Leak

Detected

P0460 Fuel Level Unit No Change Over

Miles
P0461 Fuel Level Unit No Changeover Time No level of fuel level sender detected.
P0462 Fuel Level Sending Unit Volts Too

Low

P0463 Fuel Level Sending Unit Volts Too

High

P0500 (M) No Vehicle Speed Sensor Signal No vehicle speed sensor signal detected during road load

P0505 (M) Idle Air Control Motor Circuits Replace

P0522 Oil Pressure Sens Low Oil pressure sensor input below acceptable voltage.
P0523 Oil Pressure Sens High Oil pressure sensor input above acceptable voltage.

P0551 (M) Power Steering Switch Failure Incorrect input state detected for the power steering

P0600 (M) PCM Failure SPI Communications No communication detected between co-processors in the

P0601 (M) Internal Controller Failure Internal control module fault condition (check sum)

P0604 Internal Trans Controller Transmission control module RAM self test fault detected.

P0605 Internal Trans Controller Transmission control module ROM self test fault detected

P0622 (G) Generator Field Not Switching

Properly

P0645 A/C Clutch Relay Circuit An open or shorted condition detected in the A/C clutch

P0700 (M) EATX Controller DTC Present This SBEC III or JTEC DTC indicates that the EATX or

P0703 (M) Brake Switch Stuck Pressed or

Released

P0711 Trans Temp Sensor, No Temp Rise

After Start

A small leak has been detected in the evaporative

system.

solenoid control circuit.

A large leak has been detected in the evaporative system.

A small leak has been detected in the evaporative

system.

No movement of fuel level sender detected.

Fuel level sensor input below acceptable voltage.

Fuel level sensor input above acceptable voltage.

conditions.

switch circuit. PL: High pressure seen at high speed.

control module.

detected.

-Aisin transmission.

-Aisin transmission.

An open or shorted condition detected in the generator

field control circuit.

relay control circuit.

Aisin controller has an active fault and has illuminated the

MIL via a CCD (EATX) or SCI (Aisin) message. The

specific fault must be acquired from the EATX via CCD or

from the Aisin via ISO-9141.

Incorrect input state detected in the brake switch circuit.

(Changed from P1595).

Relationship between the transmission temperature and

overdrive operation and/or TCC operation indicates a

failure of the Transmission Temperature Sensor. OBD II

Rationality.

25 - 8 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P0712 Trans Temp Sensor Voltage Too Low Transmission fluid temperature sensor input below

acceptable voltage.

P0713 Trans Temp Sensor Voltage Too

High

P0720 Low Output SPD Sensor RPM,

Above 15 MPH

P0740 (M) Torq Con Clu, No RPM Drop at

Lockup

P0743 Torque Converter Clutch Solenoid/

Trans Relay Circuits

P0748 Governor Pressur Sol Control/Trans

Relay Circuits

P0751 O/D Switch Pressed (Lo) More Than

5 Minutes

P0753 Trans 3-4 Shift Sol/Trans Relay

Circuits

P0756 AW4 Shift Sol B (2-3) Functional

Failure

P0783 3-4 Shift Sol, No RPM Drop at

Lockup

P0801 Reverse Gear Lockout Circuit Open

or Short
P01192 Inlet Air Temp. Circuit Low Inlet Air Temp. sensor input below acceptable voltage
P01193 Inlet Air Temp. Circuit High Inlet Air Temp. sensor input above acceptable voltage.

P1195 (M) 1/1 O2 Sensor Slow During Catalyst

Monitor

P1196 (M) 2/1 O2 Sensor Slow During Catalyst

Monitor

P1197 1/2 O2 Sensor Slow During Catalyst

Monitor

P1198 Radiator Temperature Sensor Volts

Too High

P1199 Radiator Temperature Sensor Volts

Too Low

P1281 Engine is Cold Too Long Engine coolant temperature remains below normal

P1282 Fuel Pump Relay Control Circuit An open or shorted condition detected in the fuel pump

P1288 Intake Manifold Short Runner

Solenoid Circuit

P1289 Manifold Tune Valve Solenoid Circuit An open or shorted condition detected in the manifold

Transmission fluid temperature sensor input above

acceptable voltage.

The relationship between the Output Shaft Speed Sensor

and vehicle speed is not within acceptable limits.

Relationship between engine and vehicle speeds

indicated failure of torque convertor clutch lock-up system

(TCC/PTU sol).

An open or shorted condition detected in the torque

converter clutch (part throttle unlock) solenoid control

circuit. Shift solenoid C electrical fault - Aisin transmission

An open or shorted condition detected in the Governor

Pressure Solenoid circuit or Trans Relay Circuit in JTEC

RE transmissions.

Overdrive override switch input is in a prolonged

depressed state.

An open or shorted condition detected in the overdrive

solenoid control circuit or Trans Relay Circuit in JTEC RE

transmissions.

Shift solenoid B (2-3) functional fault - Aisin transmission

The overdrive solenoid is unable to engage the gear

change from 3rd gear to the overdrive gear.

An open or shorted condition detected in the transmission

reverse gear lock-out solenoid control circuit.

A slow switching oxygen sensor has been detected in

bank 1/1 during catalyst monitor test. (was P0133)

A slow switching oxygen sensor has been detected in

bank 2/1 during catalyst monitor test. (was P0153)

A slow switching oxygen sensor has been detected in

bank 1/2 during catalyst monitor test. (was P0139)

Radiator coolant temperature sensor input above the

maximum acceptable voltage.

Radiator coolant temperature sensor input below the

minimum acceptable voltage.

operating temperatures during vehicle travel (Thermostat).

relay control circuit.

An open or shorted condition detected in the short runner

tuning valve circuit.

tuning valve solenoid control circuit.

NS EMISSION CONTROL SYSTEMS 25 - 9

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P1290 CNG Fuel System Pressure Too

High

P1291 No Temp Rise Seen From Intake

Heaters

P1292 CNG Pressure Sensor Voltage Too

High

P1293 CNG Pressure Sensor Voltage Too

Low

P1294 (M) Target Idle Not Reached Target RPM not achieved during drive idle condition.

P1295 No 5 Volts to TP Sensor Loss of a 5 volt feed to the Throttle Position Sensor has

P1296 No 5 Volts to MAP Sensor Loss of a 5 volt feed to the MAP Sensor has been

P1297 (M) No Change in MAP From Start To

Run

P1298 Lean Operation at Wide Open

Throttle

P1299 (M) Vacuum Leak Found (IAC Fully

Seated)

P1388 Auto Shutdown Relay Control Circuit An open or shorted condition detected in the ASD or CNG

P1389 No ASD Relay Output Voltage At

PCM
P1390 (M) Timing Belt Skipped 1 Tooth or More Relationship between Cam and Crank signals not correct.
P1391 (M) Intermittent Loss of CMP or CKP Loss of the Cam Position Sensor or Crank Position

P1398 (M) Mis-Fire Adaptive Numerator at Limit PCM is unable to learn the Crank Sensor’s signal in

P1399 Wait To Start Lamp Cicuit An open or shorted condition detected in the Wait to Start

P1403 No 5 Volts to EGR Sensor Loss of 5v feed to the EGR position sensor.
P1476 Too Little Secondary Air Insufficient flow of secondary air injection detected during

P1477 Too Much Secondary Air Excessive flow of secondary air injection detected during

P1478 (M) Battery Temp Sensor Volts Out of

Limit

P1479 Transmission Fan Relay Circuit An open or shorted condition detected in the transmission

P1480 PCV Solenoid Circuit An open or shorted condition detected in the PCV

P1482 Catalyst Temperature Sensor Circuit

Shorted Low

Compressed natural gas system pressure above normal

operating range.

Energizing Heated Air Intake does not change intake air

temperature sensor an acceptable amount.

Compressed natural gas pressure sensor reading above

acceptable voltage.

Compressed natural gas pressure sensor reading below

acceptable voltage.

Possible vacuum leak or IAC (AIS) lost steps.

been detected.

detected.

No difference is recognized between the MAP reading at

engine idle and the stored barometric pressure reading.

A prolonged lean condition is detected during Wide Open

Throttle.

MAP Sensor signal does not correlate to Throttle Position

Sensor signal. Possible vacuum leak.

shutoff relay control ckt.

No Z1 or Z2 voltage sensed when the auto shutdown

relay is energized.

sensor has occurred. For PL 2.0L

preparation for Misfire Diagnostics. Probable defective

Crank Sensor.

Lamp circuit.

aspirator test.(was P0411)

aspirator test (was P0411).

Internal temperature sensor input voltage out of an

acceptable range.

fan relay circuit.

solenoid circuit.

Catalyst temperature sensor circuit shorted low.

25 - 10 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P1483 Catalyst Temperature Sensor Circuit

Shorted High.

P1484 Catalytic Converter Overheat

Detected

P1485 Air Injection Solenoid Circuit An open or shorted condition detected in the air assist

P1486 (M) Evap Leak Monitor Pinched Hose

Found

P1487 Hi Speed Rad Fan CTRL Relay

Circuit

P1488 Auxiliary 5 Volt Supply Output Too

Low

P1489 (M) High Speed Fan CTRL Relay Circuit An open or shorted condition detected in the control

P1490 (M) Low Speed Fan CTRL Relay Circuit An open or shorted condition detected in control circuit of

P1491 Rad Fan Control Relay Circuit An open or shorted condition detected in the radiator fan

P1492 (M,G) Ambient/Batt Temp Sen Volts Too

High

P1493 (M,G) Ambient/Batt Temp Sen Volts Too

Low

P1494 (M) Leak Detection Pump Sw or

Mechanical Fault

P1495 (M) Leak Detection Pump Solenoid

Circuit

P1496 (M) 5 Volt Supply, Output Too Low 5 volt sensor feed is sensed to be below an acceptable

P1498 High Speed Rad Fan Ground CTRL

Rly Circuit

P1594 (G) Charging System Voltage Too High Battery voltage sense input above target charging voltage

P1595 Speed Control Solenoid Circuits An open or shorted condition detected in either of the

P1596 Speed Control Switch Always High Speed control switch input above maximum acceptable

P1597 Speed Control Switch Always Low Speed control switch input below minimum acceptable

P1598 A/C Pressure Sensor Volts Too High A/C pressure sensor input above maximum acceptable

P1599 A/C Pressure Sensor Volts Too Low A/C pressure sensor input below minimum acceptable

P1680 Clutch Released Switch Circuit
P1681 No I/P Cluster CCD/J1850

Messages Received

Catalyst temperature sensor circuit shorted high.

A catalyst overheat condition has been detected by the

catalyst temperature sensor.

solenoid circuit.

LDP has detected a pinched hose in the evaporative hose

system.

An open or shorted condition detected in the control

circuit of the #2 high speed radiator fan control relay.

Auxiliary 5 volt sensor feed is sensed to be below an

acceptable limit.

circuit of the high speed radiator fan control relay.

the low speed radiator fan control relay.

control relay control circuit. This includes PWM solid state

relays.

External temperature sensor input above acceptable

voltage.

External temperature sensor input below acceptable

voltage.

Incorrect input state detected for the Leak Detection

Pump (LDP) pressure switch.

An open or shorted condition detected in the Leak

Detection Pump (LDP) solenoid circuit.

limit.(<4vfor4sec).

An open or shorted condition detected in the control

circuit of the #3 high speed radiator fan control relay.

during engine operation.

speed control vacuum or vent solenoid control circuits.

voltage.

voltage.

voltage.

voltage.

No CCD/J1850 messages received from the cluster

control module.

NS EMISSION CONTROL SYSTEMS 25 - 11

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P1682 (G) Charging System Voltage Too Low Battery voltage sense input below target charging voltage

during engine operation and no significant change in

voltage detected during active test of generator output

circuit.

P1683 SPD CTRL PWR Relay; or S/C 12v

Driver CKT

P1684 The battery has been disconnected within the last 50

P1685 Skim Invalid Key The engine controler has received an invalid key from the

P1686 No SKIM BUS Messages Received No CCD/J1850 messages received from the Smart Key

P1687 No MIC BUS Message No CCD/J1850 messages received from the Mechanical

P1693 DTC Detected in Companion Module A fault has been generated in the companion engine

P1694 Fault In Companion Module No CCD/J1850 messages received from the powertrain

P1695 No CCD/J1850 Message From Body

Control Module

P1696 (M) PCM Failure EEPROM Write Denied Unsuccessful attempt to write to an EEPROM location by

P1697 (M) PCM Failure SRI Mile Not Stored Unsuccessful attempt to update Service Reminder

P1698 (M) No CCD/J1850 Message From TCM No CCD/J1850 messages received from the electronic

P1719 Skip Shift Solenoid Circuit An open or shorted condition detected in the transmission

P1756 GOV Press Not Equal to Target @

15-20 PSI

P1757 GOV Press Not Equal to Target @

15-20 PSI

P1762 Gov Press Sen Offset Volts Too Lo

or High

P1763 Governor Pressure Sensor Volts Too

Hi

P1764 Governor Pressure Sensor Volts Too

Low

An open or shorted condition detected in the speed

control servo power control circuit. (SBECII: ext relay).

starts.

SKIM.

Immobilizer Module (SKIM).

Instrument Cluster (MIC) module.

control module.

control module-Aisin transmission.

No CCD/J1850 messages received from the body control

module.

the control module.

Indicator (SRI or EMR) mileage in the control module

EEPROM.

transmission control module (EATX) or the Aisin

transmission controller.

2-3 gear lock-out solenoid control circuit.

The requested pressure and the actual pressure are not

within a tolerance band for the Governor Control System

which is used to regulate governor pressure to control

shifts for 1st, 2nd, and 3rd gear. (Mid Pressure

Malfunction)

The requested pressure and the actual pressure are not

within a tolerance band for the Governor Control System

which is used to regulate governor pressure to control

shifts for 1st, 2nd, and 3rd gear (Zero Pressure

Malfunction)

The Governor Pressure Sensor input is greater than a

calibration limit or is less than a calibration limit for 3

consecutive park/neutral calibrations.

The Governor Pressure Sensor input is above an

acceptable voltage level.

The Governor Pressure Sensor input is below an

acceptable voltage level.

25 - 12 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.

(G) Generator Lamp Illuminated

P1765 Trans 12 Volt Supply Relay CTRL

Circuit

P1899 (M) P/N Switch Stuck in Park or in Gear Incorrect input state detected for the Park/Neutral switch.

An open or shorted condition is detected in the

Transmission Relay control circuit. This relay supplies

power to the TCC>

MONITORED SYSTEMS

DESCRIPTION

There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor­mance. These monitors use information from various
sensor circuits to indicate the overall operation of the
fuel, engine, ignition and emission systems and thus
the emissions performance of the vehicle.

The fuel, engine, ignition and emission systems
monitors do not indicate a specific component prob­lem. They do indicate that there is an implied prob­lem within one of the systems and that a specific
problem must be diagnosed.

If any of these monitors detect a problem affecting
vehicle emissions, the Malfunction Indicator (Check
Engine) Lamp will be illuminated. These monitors
generate Diagnostic Trouble Codes that can be dis­played with the check engine lamp or a scan tool.

The following is a list of the monitored systems:

• EGR Monitor

• Misfire Monitor

• Fuel System Monitor

• Evaporative Emissions Monitor

Following is a description of each system monitor,
and its DTC.

Refer to the appropriate Powertrain Diagnos­tics Procedures manual for diagnostic proce­dures.

EGR MONITOR

The Powertrain Control Module (PCM) performs
an on-board diagnostic check of the EGR system.

The EGR system consists of two main components:
a vacuum solenoid back pressure transducer and a
vacuum operated valve. The EGR monitor is used to
test whether the EGR system is operating within
specifications. The diagnostic check activates only
during selected engine/driving conditions. When the
conditions are met, the EGR is turned off (solenoid
energized) and the O2S compensation control is mon­itored. Turning off the EGR shifts the air fuel (A/F)
ratio in the lean direction. Oxygen sensor voltage
then indicates increased oxygen in the exhaust. Con­sequently, Short Term Compensation shifts to rich
(increased injector pulse width). By monitoring the

shift, the PCM can indirectly monitor the EGR sys­tem. While this test does not directly measure the
operation of the EGR system, it can be inferred from
the shift in the O2S data whether the EGR system is
operating correctly. Because the O2S is being used,
the O2S test must pass its test before the EGR test.

Enabling Conditions—

• Engine Temperature

• Engine Run Time

• Engine RPM

• MAP Sensor

• TPS

• Vehicle Speed

• Short Term Compensation

Pending Conditions— The EGR Monitor does
not run when any of the following example faults
have illuminated the MIL:

• Misfire

• Oxygen Sensor Monitor

• Oxygen Sensor Heater Monitor

• Fuel System Rich/Lean

• Limp in for MAP, TPS or ECT

• Vehicle Speed Sensor

• Cam or Crank Sensor

• EGR Electrical

• EVAP Electrical

• Fuel Injector

• Ignition Coil

• Idle Speed

• Engine Coolant Temperature (ECT)

• MAP Sensor

• Intake Air Temperature (IAT)

Conflict Conditions— The EGR Monitor typi­cally does not run if any of the following conditions
are present:

• Fuel System Monitor

• Purge Monitor

• Catalyst Monitor

• Low Fuel Level

• High Altitude

• Low Ambient Air Temperature

The EGR Monitor does not run if any of the follow­ing example DTCs are present:

• Misfire Monitor, Priority 2

• Upstream Oxygen Sensor Heater, Priority 1

• Fuel System Monitor, Priority 2

• Oxygen Sensor Monitor, Priority 1

NS EMISSION CONTROL SYSTEMS 25 - 13

DESCRIPTION AND OPERATION (Continued)

MISFIRE MONITOR

Excessive engine misfire results in increased cata­lyst temperature and causes an increase in HC emis­sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.

The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank­shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.

OBD II regulations for misfire monitoring require
two different tests for misfire. The first is a Catalyst
Damage level of misfire test. The second is for emis­sions greater than 1.5 times the Federal Tailpipe
(FTP) standards. The tests are monitored by two dif­ferent counters. These counters are:

• 200 revolution increments for immediate cata-

lyst damage

• 1000 revolution increments for emissions viola-

tion and Inspection/Maintenance (I/M) test failure

NOTE: The percent of misfire for malfunction crite­ria varies due to RPM and load. As the engine
speed increases or load decreases, the effects of a
misfire diminishes due to crankshaft momentum.
Failure percentages also vary from engine to
engine.

Monitor Operation— The PCM utilizes the
Crankshaft Speed Fluctuation method to monitor for
misfire. The misfire monitor utilizes a crankshaft
position sensor to determine engine RPM. The sensor
can detect slight variations in engine speed due to
misfire. Misfire is continuously monitored once the
enabling conditions are met.

Once enabling conditions are met, the PCM counts
the number of misfires in every 200 revolutions of
the crankshaft. If, during five 200 counters, the mis­fire percentage exceeds a predetermined value, a
maturing code is set and a Freeze Frame is entered.
Freeze Frame data is recorded during the last 200
revolutions of the 1000 revolution period. A failure on
the second consecutive trip matures the code and a
DTC is set.

If misfire continues during the initial trip, the MIL
is not illuminated. However, the MIL flashes when
the misfire percentage exceeds the malfunction per­centage, in any 200 revolution period, that would
cause permanent catalyst damage. This is a one trip
monitor. If misfire reaches a point in which catalyst
damage is likely to occur, the MIL flashes and a DTC
is stored in a Freeze Frame. The engine defaults to
open loop operation to prevent increased fuel flow to
the cylinders. Once misfire is below the predeter­mined percentage, the MIL stops flashing but
remains illuminated.

The 1000 revolution counters are two trip moni­tors. As with the fuel system monitor, Freeze Frame
data is from the original fault, and MIL extinguish­ing requires the monitor to pass under similar condi­tions.

The Adaptive Numerator— The Misfire Monitor
takes into account component wear, sensor fatigue
and machining tolerances. The PCM compares the
crankshaft in the vehicle to data on an ideal crank
and uses this as a basis to determine variance. To do
this, the crankshaft sensor monitors the reference
notches in the crank. The PCM uses the first signal
set as a point of reference. It then measures where
the second set of signals is, compared to where engi­neering data has determined it should be. This vari­ance is the Adaptive Numerator. The monitor will not
run if the numerator is not set.

If the Adaptive Numerator is equal to the default
value, the adaptive Numerator has not been learned
and the Misfire Monitor does not run. If the Adaptive
Numerator exceeds its limits, the PCM sets a DTC
for Adaptive Numerator and illuminates the MIL.

RPM Error— The PCM also checks the machining
tolerances for each group of slots. By monitoring the
speed of the crank from the first slot to the last slot
in a group, the PCM can calculate engine RPM. The
variance between groups of slots is know as the RPM
error. In order for the PCM to run the Misfire Mon­itor, RPM error must be less than approximately 5%.

Enabling Conditions— The following conditions
must be met before the PCM runs the Misfire Moni­tor:

• RPM

• Engine Coolant Temperature (ECT)

• Barometric Pressure (MAP)

• Fuel level

• Ambient air Temperature

Pending Conditions— The Misfire Monitor does
not run when the MIL is illuminated for any of the
following:

• Limp in mode for
— MAP
— TPS
— Crankshaft Sensor
— Engine Coolant Temperature Sensor

• Speed Sensor DTC

• EGR Electrical

• EVAP Electrical

• Idle Speed Faults

• Intake Air Temperature

• Oxygen Sensor Monitor

• Oxygen Sensor Electrical

Conflict Conditions— If any of the following con­ditions conflict with the Misfire Monitor, the monitor
will not run:

• Low fuel level

25 - 14 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

• MAP voltage rapidly changing

• Severe engine decel

• TPS toggling OPEN/CLOSED

• Engine RPM too low (RPM levels by vehicle)

• Engine RPM too high (RPM levels vary by vehi-

cle)

• Full Lean or Decel Fuel Shut-off

• Cold start

FUEL SYSTEM MONITOR

To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro­gen and carbon monoxide. The catalyst works best
when the air fuel (A/F) ratio is at or near the opti­mum of 14.7 to 1.

The PCM is programmed to maintain the optimum
air/fuel ratio of 14.7 to 1. This is done by making
short term corrections in the fuel injector pulse width
based on the O2S output. The programmed memory
acts as a self calibration tool that the engine control­ler uses to compensate for variations in engine spec­ifications, sensor tolerances and engine fatigue over
the life span of the engine. By monitoring the actual
air-fuel ratio with the O2S (short term) and multiply­ing that with the program long-term (adaptive) mem­ory and comparing that to the limit, it can be
determined whether it will pass an emissions test. If
a malfunction occurs such that the PCM cannot
maintain the optimum A/F ratio, then the MIL will
be illuminated.

Monitor Operation— Fuel systems monitors do
not have a pre-test because they are continuously
running monitors. Therefore, the PCM constantly
monitors Short Term Compensation and Long Term
Adaptive memory.

Lean: If at anytime during a lean engine operation,
short term compensation multiplied by long term
adaptive exceeds a certain percentage for an
extended period, the PCM sets a Fuel System Lean
Fault for that trip and a Freeze Frame is entered.

Rich: If at anytime during a rich operation, Short
Term Compensation multiplied by Long Term Adap­tive is less than a predetermined value, the PCM
checks the Purge Free Cells.

Purge Free Cells are values placed in Adaptive
Memory cells when the EVAP Purge Solenoid is OFF.
Two, three or four Purge Free cells are used. One cor­responds to an Adaptive Memory cell at idle, the
other to a cell that is off-idle. For example, if a Purge
Free cell is labeled PFC1, it would hold the value for
Adaptive Memory cell C1 under non-purge condi­tions.

If all Purge Free Cells are less than a certain per­centage, and the Adaptive Memory factor is less than
a certain percentage, the PCM sets a Fuel System

Rich fault for that trip and a Freeze Frame is
entered.

The Fuel Monitor is a two trip monitor. The PCM
records engine data in Freeze Frame upon setting of
the first fault, or maturing code. When the fuel mon­itor fails on a second consecutive trip, the code is
matured and the MIL is illuminated. The stored
Freeze Frame data is still from the first fault.

In order for the PCM to extinguish the MIL, the
Fuel Monitor must pass in a Similar Condition Win­dow. The similar conditions relate to RPM and load.
The engine must be within a predetermined percent­age of both RPM and load when the monitor runs to
count a good trip. As with all DTCs, three good trips
are required to extinguish the MIL and 40 warm up
cycles are required to erase the DTC. If the engine
does not run in a Similar Conditions Window, the
Task Manager extinguishes the MIL after 80 good
trips.

Enabling Conditions— The following conditions
must be met to operate the fuel control monitor:

• PCM not in fuel crank mode (engine running)

• PCM in Closed Loop fuel control

• Fuel system updating Long Term Adaptive

• Fuel level above 15% of capacity

• Fuel level below 85% of capacity

Pending Conditions— The Fuel Control Monitor
does not operate if the MIL is illuminated for any of
the following:

• Misfire Monitor

• Upstream O2S

• EVAP Purge Solenoid Electrical PCM Self Test

Fault

• Camshaft or Crankshaft Position Sensor

• Fuel Injectors

• Ignition Coil Primary

• Throttle Position (TPS) Sensor

• Engine Coolant Temperature (ECT) Sensor

• Manifold Absolute Pressure (MAP) Sensor

• Idle Air Control (IAC)

• 5V Output Too Low

• EGR Monitor

• EGR Solenoid Circuit

• Vehicle Speed Sensor

• Oxygen Sensor Monitor

• Oxygen Sensor Heater Monitor

• Oxygen Sensor Electrical

• Idle Speed Rationality

• Intake Air Temperature

Suspend— The Task Manager will suspend
maturing a Fuel System fault if any of the following
are present:

• Oxygen Sensor Response, Priority 1

• O2 Heater, Priority 1

• Misfire Monitor, Priority 2

NS EMISSION CONTROL SYSTEMS 25 - 15

DESCRIPTION AND OPERATION (Continued)

EVAPORATIVE EMISSIONS MONITOR

LEAK DETECTION PUMP MONITOR— The
leak detection assembly incorporates two primary
functions: it must detect a leak in the evaporative
system and seal the evaporative system so the leak
detection test can be run.

The primary components within the assembly are:
A three port solenoid that activates both of the func­tions listed above; a pump which contains a switch,
two check valves and a spring/diaphragm, a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.

Immediately after a cold start, between predeter­mined temperature thresholds limits, the three port
solenoid is briefly energized. This initializes the
pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi­tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia­phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con­trolled in 2 modes:

Pump Mode: The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.

Test Mode: The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.

The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5” H20.
The cycle rate of pump strokes is quite rapid as the
system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even­tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep­resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur­rently set at.040” orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.

After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP’s solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle

rate is again interrogated and when it increases due
to the flow through the purge system, the leak check
portion of the diagnostic is complete.

The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.

Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.

Enabling Conditions for Systems with LDP

• Ambient Air Temperature

• Barometric Pressure

• Fuel level

• Engine Temperature

• No stalling

• Battery voltage

NON-LDP VEHICLES— On a vehicle without an
EVAP leak detection pump system, changes in short
term memory and movement in target IAC at idle or
idle speed change, are used to monitor the system.
There are two stages for this test.

Stage One— Stage one is a non-intrusive test.
The PCM compares adaptive memory values between
purge and purge-free cells. The PCM uses these val­ues to determine the amount of fuel vapors entering
the system. If the difference between the cells
exceeds a predetermined value, the test passes. If
not, then the monitor advances to state two.

Stage Two— Once the enabling conditions are
met, the PCM de-energizes the Duty Cycle Purge
(DCP) solenoid. The PCM then waits until engine
RPM, Short Term Compensation and Idle Air Control
have all stabilized. Once stable, the PCM increments
the DCP solenoid cycle rate approximately 6% every
8 engine revolutions. If during the test any one of
three conditions occur before the DCP cycle reaches
100%, the EVAP system is considered to be opera­tional and the test passes. These conditions are as
follows:

• RPM rises by a predetermined amount

• Short Term drops by a predetermined amount

• Idle Air Control closes by a predetermined

amount

When none of the previous conditions occur, the
test fails and the PCM increments a counter by one.
When the PCM runs the test three times during a
trip, and the counter has been incremented to three,
the monitor fails and a Freeze Frame is stored.

25 - 16 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

Enabling Conditions (Stage Two)— The follow­ing conditions must be met to enable the EVAP Mon­itor (without LDP)

• Ambient Air Temperature

• Barometric Pressure

• Fuel level

• Engine Temperature

• Engine run time

• RPM stable

• MAP

• Generator, radiator fans, A/C clutch

Pending Conditions-With or Without LDP—

The EVAP Monitor is suspended and does not run,
when the MIL is illuminated due to any of the fol­lowing faults:

• Misfire

• Oxygen Sensor Monitor

• Fuel System Rich

• Fuel System Lean

• EGR Monitor

• MAP

• TPS

• ECT

• DCP Solenoid

Conflict Conditions-With or Without LDP—

The EVAP Monitor does not run if any of the follow­ing tests are in progress:

• Catalyst

• EGR

• Fuel System

• Misfire

TRIP DEFINITION

OPERATION

A “Trip” means vehicle operation (following an
engine-off period) of duration and driving mode such
that all components and systems are monitored at
least once by the diagnostic system. The monitors
must successfully pass before the PCM can verify
that a previously malfunctioning component is meet­ing the normal operating conditions of that compo­nent. For misfire or fuel system malfunction, the
MIL may be extinguished if the fault does not recur
when monitored during three subsequent sequential
driving cycles in which conditions are similar to
those under which the malfunction was first deter­mined.

Anytime the MIL is illuminated, a DTC is stored.
The DTC can self erase only when the MIL has been
extinguished. Once the MIL is extinguished, the
PCM must pass the diagnostic test for the most
recent DTC for 40 warm-up cycles (80 warm-up
cycles for the Fuel System Monitor and the Misfire
Monitor). A warm-up cycle can best be described by
the following:

• The engine must be running

• A rise of 40°F in engine temperature must occur

from the time when the engine was started

• Engine coolant temperature must reach at least

160°F

• A “driving cycle” that consists of engine start up

and engine shut off.

Once the above conditions occur, the PCM is con­sidered to have passed a warm-up cycle. Due to the
conditions required to extinguish the MIL and erase
the DTC, it is most important that after a repair has
been made, all DTC’s be erased and the repair veri­fied.

MONITORED COMPONENT

DESCRIPTION

There are several components that will affect vehi­cle emissions if they malfunction. If one of these com­ponents malfunctions the Malfunction Indicator
Lamp (Check Engine) will illuminate.

Some of the component monitors are checking for
proper operation of the part. Electrically operated
components now have input (rationality) and output
(functionality) checks. Previously, a component like
the Throttle Position sensor (TPS) was checked by
the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there
is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
greater or lesser throttle opening than MAP and
engine rpm indicate. In the case of the TPS, if engine
vacuum is high and engine rpm is 1600 or greater
and the TPS indicates a large throttle opening, a
DTC will be set. The same applies to low vacuum
and 1600 rpm.

Any component that has an associated limp in will
set a fault after 1 trip with the malfunction present.

Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Power­train Diagnostic Procedure Manual for diagnostic
procedures.

The following is a list of the monitored compo­nents:

• Comprehensive Components

• Oxygen Sensor Monitor

• Oxygen Sensor Heater Monitor

• Catalyst Monitor

COMPREHENSIVE COMPONENTS

Along with the major monitors, OBD II requires
that the diagnostic system monitor any component
that could affect emissions levels. In many cases,
these components were being tested under OBD I.
The OBD I requirements focused mainly on testing

NS EMISSION CONTROL SYSTEMS 25 - 17

DESCRIPTION AND OPERATION (Continued)

emissions-related components for electrical opens and
shorts.

However, OBD II also requires that inputs from
powertrain components to the PCM be tested for
rationality, and that outputs to powertrain compo­nents from the PCM be tested for functionality.
Methods for monitoring the various Comprehensive
Component monitoring include:

(1) Circuit Continuity

• Open

• Shorted high

• Shorted to ground

(2) Rationality or Proper Functioning

• Inputs tested for rationality

• Outputs tested for functionality

NOTE: Comprehensive component monitors are
continuous. Therefore, enabling conditions do not
apply.

Input Rationality— While input signals to the
PCM are constantly being monitored for electrical
opens and shorts, they are also tested for rationality.
This means that the input signal is compared against
other inputs and information to see if it makes sense
under the current conditions.

PCM sensor inputs that are checked for rationality
include:

• Manifold Absolute Pressure (MAP) Sensor

• Oxygen Sensor (O2S)

• Engine Coolant Temperature (ECT) Sensor

• Camshaft Position (CMP) Sensor

• Vehicle Speed Sensor

• Crankshaft Position (CKP) Sensor

• Intake Air Temperature (IAT) Sensor

• Throttle Position (TPS) Sensor

• Ambient/Battery Temperature Sensors

• Power Steering Switch

• Oxygen Sensor Heater

• Engine Controller

• Brake Switch

• Leak Detection Pump Switch

• P/N Switch

• Trans Controls

Output Functionality— PCM outputs are tested
for functionality in addition to testing for opens and
shorts. When the PCM provides a voltage to an out­put component, it can verify that the command was
carried out by monitoring specific input signals for
expected changes. For example, when the PCM com­mands the Idle Air Control (IAC) Motor to a specific
position under certain operating conditions, it expects
to see a specific (target) idle speed (RPM). If it does
not, it stores a DTC.

PCM outputs monitored for functionality include:

• Fuel Injectors

• Ignition Coils

• Torque Converter Clutch Solenoid

• Idle Air Control

• Purge Solenoid

• EGR Solenoid

• LDP Solenoid

• Radiator Fan Control

• Trans Controls

OXYGEN SENSOR (O2S) MONITOR

DESCRIPTION— Effective control of exhaust
emissions is achieved by an oxygen feedback system.
The most important element of the feedback system
is the O2S. The O2S is located in the exhaust path.
Once it reaches operating temperature 300° to 350°C
(572° to 662°F), the sensor generates a voltage that
is inversely proportional to the amount of oxygen in
the exhaust. When there is a large amount of oxygen
in the exhaust caused by a lean condition, the sensor
produces a low voltage, below 450 mV. When the oxy­gen content is lower, caused by a rich condition, the
sensor produces a higher voltage, above 450mV.

The information obtained by the sensor is used to
calculate the fuel injector pulse width. This main­tains a 14.7 to 1 air fuel (A/F) ratio. At this mixture
ratio, the catalyst works best to remove hydrocarbons
(HC), carbon monoxide (CO) and nitrous oxide (NOx)
from the exhaust.

The O2S is also the main sensing element for the
EGR, Catalyst and Fuel Monitors.

The O2S may fail in any or all of the following
manners:

• Slow response rate (Big Slope)

• Reduced output voltage (Half Cycle)

• Heater Performance

Slow Response Rate (Big Slope)— Response
rate is the time required for the sensor to switch
from lean to rich signal output once it is exposed to a
richer than optimum A/F mixture or vice versa. As
the PCM adjusts the air/fuel ratio, the sensor must
be able to rapidly detect the change. As the sensor
ages, it could take longer to detect the changes in the
oxygen content of the exhaust gas. The rate of
change that an oxygen sensor experiences is called
’Big Slope’. The PCM checks the oxygen sensor volt­age in increments of a few milliseconds.

Reduced Output Voltage (Half Cycle)— The
output voltage of the O2S ranges from 0 to 1 volt. A
good sensor can easily generate any output voltage in
this range as it is exposed to different concentrations
of oxygen. To detect a shift in the A/F mixture (lean
or rich), the output voltage has to change beyond a
threshold value. A malfunctioning sensor could have
difficulty changing beyond the threshold value. Each
time the voltage signal surpasses the threshold, a
counter is incremented by one. This is called the Half
Cycle Counter.

25 - 18 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

Heater Performance— The heater is tested by a
separate monitor. Refer to the Oxygen Sensor Heater
Monitor.

OPERATION— As the Oxygen Sensor signal
switches, the PCM monitors the half cycle and big
slope signals from the oxygen sensor. If during the
test neither counter reaches a predetermined value, a
malfunction is entered and a Freeze Frame is stored.
Only one counter reaching its predetermined value is
needed for the monitor to pass.

The Oxygen Sensor Monitor is a two trip monitor
that is tested only once per trip. When the Oxygen
Sensor fails the test in two consecutive trips, the
MIL is illuminated and a DTC is set. The MIL is
extinguished when the Oxygen Sensor monitor
passes in three consecutive trips. The DTC is erased
from memory after 40 consecutive warm-up cycles
without test failure.

Enabling Conditions— The following conditions
must typically be met for the PCM to run the oxygen
sensor monitor:

• Battery voltage

• Engine temperature

• Engine run time

• Engine run time at a predetermined speed

• Engine run time at a predetermined speed and

throttle opening

• Transmission in gear (automatic only)

• Fuel system in Closed Loop

• Long Term Adaptive (within parameters)

• Power Steering Switch in low PSI (no load)

• Engine at idle

• Fuel level above 15%

• Ambient air temperature

• Barometric pressure

• Engine RPM within acceptable range of desired

idle

• Closed throttle speed

Pending Conditions— The Task Manager typi­cally does not run the Oxygen Sensor Monitor if over­lapping monitors are running or the MIL is
illuminated for any of the following:

• Misfire Monitor

• Front Oxygen Sensor and Heater Monitor

• MAP Sensor

• Vehicle Speed Sensor

• Engine Coolant Temperature Sensor

• Throttle Position Sensor

• Engine Controller Self Test Faults

• Cam or Crank Sensor

• Injector and Coil

• Idle Air Control Motor

• EVAP Electrical

• EGR Solenoid Electrical

• Intake Air Temperature

• 5 Volt Feed

Conflict— The Task Manager does not run the
Oxygen Sensor Monitor if any of the following condi­tions are present:

• A/C ON (A/C clutch cycling temporarily sus-

pends monitor)

• Purge flow in progress

Suspend— The Task Manager suspends maturing
a fault for the Oxygen Sensor Monitor if an of the fol­lowing are present:

• Oxygen Sensor Heater Monitor, Priority 1

• Misfire Monitor, Priority 2

OXYGEN SENSOR HEATER MONITOR

DESCRIPTION— If there is an oxygen sensor
(O2S) DTC as well as a O2S heater DTC, the O2S
fault MUST be repaired first. After the O2S fault is
repaired, verify that the heater circuit is operating
correctly.

The voltage readings taken from the O2S are very
temperature sensitive. The readings are not accurate
below 300°C. Heating of the O2S is done to allow the
engine controller to shift to closed loop control as
soon as possible. The heating element used to heat
the O2S must be tested to ensure that it is heating
the sensor properly.

The heater element itself is not tested. The sensor
output is used to test the heater by isolating the
effect of the heater element on the O2S output volt­age from the other effects. The resistance is normally
between 100 ohms and 4.5 megaohms. When oxygen
sensor temperature increases, the resistance in the
internal circuit decreases. The PCM sends a 5 volts
biased signal through the oxygen sensors to ground
this monitoring circuit. As the temperature increases,
resistance decreases and the PCM detects a lower
voltage at the reference signal. Inversely, as the tem­perature decreases, the resistance increases and the
PCM detects a higher voltage at the reference signal.
an The O2S circuit is monitored for a drop in voltage.

OPERATION— The Oxygen Sensor Heater Moni­tor begins after the ignition has been turned OFF
and the O2 sensors have cooled. The PCM sends a 5
volt bias to the oxygen sensor every 1.6 seconds. The
PCM keeps it biased for 35 ms each time. As the sen­sor cools down, the resistance increases and the PCM
reads the increase in voltage. Once voltage has
increased to a predetermined amount, higher than
when the test started, the oxygen sensor is cool
enough to test heater operation.

When the oxygen sensor is cool enough, the PCM
energizes the ASD relay. Voltage to the O2 sensor
begins to increase the temperature. As the sensor
temperature increases, the internal resistance
decreases. The PCM continues biasing the 5 volt sig­nal to the sensor. Each time the signal is biased, the
PCM reads a voltage decrease. When the PCM

NS EMISSION CONTROL SYSTEMS 25 - 19

DESCRIPTION AND OPERATION (Continued)

detects a voltage decrease of a predetermined value
for several biased pulses, the test passes.

The heater elements are tested each time the
engine is turned OFF if all the enabling conditions
are met. If the monitor fails, the PCM stores a
maturing fault and a Freeze Frame is entered. If two
consecutive tests fail, a DTC is stored. Because the
ignition is OFF, the MIL is illuminated at the begin­ning of the next key cycle.

Enabling Conditions— The following conditions
must be met for the PCM to run the oxygen sensor
heater test:

• Engine run time of at least 5.1 minutes

• Key OFF power down

• Battery voltage of at least 10 volts

• Sufficient Oxygen Sensor cool down

Pending Conditions— There are not conditions
or situations that prompt conflict or suspension of
testing. The oxygen sensor heater test is not run
pending resolution of MIL illumination due to oxygen
sensor failure.

Suspend— There are no conditions which exist for
suspending the Heater Monitor.

CATALYST MONITOR

To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro­gen and carbon monoxide.

Normal vehicle miles or engine misfire can cause a
catalyst to decay. A meltdown of the ceramic core can
cause a reduction of the exhaust passage. This can
increase vehicle emissions and deteriorate engine
performance, driveability and fuel economy.

The catalyst monitor uses dual oxygen sensors
(O2S’s) to monitor the efficiency of the converter. The
dual O2S strategy is based on the fact that as a cat­alyst deteriorates, its oxygen storage capacity and its
efficiency are both reduced. By monitoring the oxy­gen storage capacity of a catalyst, its efficiency can
be indirectly calculated. The upstream O2S is used to
detect the amount of oxygen in the exhaust gas
before the gas enters the catalytic converter. The
PCM calculates the A/F mixture from the output of
the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content
of oxygen (rich mixture).

When the upstream O2S detects a lean condition,
there is an abundance of oxygen in the exhaust gas.
A functioning converter would store this oxygen so it
can use it for the oxidation of HC and CO. As the
converter absorbs the oxygen, there will be a lack of
oxygen downstream of the converter. The output of
the downstream O2S will indicate limited activity in
this condition.

As the converter loses the ability to store oxygen,
the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
chemical reaction takes place. This means the con­centration of oxygen will be the same downstream as
upstream. The output voltage of the downstream
O2S copies the voltage of the upstream sensor. The
only difference is a time lag (seen by the PCM)
between the switching of the O2S’s.

To monitor the system, the number of lean-to-rich
switches of upstream and downstream O2S’s is
counted. The ratio of downstream switches to
upstream switches is used to determine whether the
catalyst is operating properly. An effective catalyst
will have fewer downstream switches than it has
upstream switches i.e., a ratio closer to zero. For a
totally ineffective catalyst, this ratio will be one-to­one, indicating that no oxidation occurs in the device.

The system must be monitored so that when cata­lyst efficiency deteriorates and exhaust emissions
increase to over the legal limit, the MIL (check
engine lamp) will be illuminated.

Monitor Operation— To monitor catalyst effi­ciency, the PCM expands the rich and lean switch
points of the heated oxygen sensor. With extended
switch points, the air/fuel mixture runs richer and
leaner to overburden the catalytic converter. Once
the test is started, the air/fuel mixture runs rich and
lean and the O2 switches are counted. A switch is
counted when an oxygen sensor signal goes from
below the lean threshold to above the rich threshold.
The number of Rear O2 sensor switches is divided by
the number of Front O2 sensor switches to determine
the switching ratio.

The test runs for 20 seconds. As catalyst efficiency
deteriorated over the life of the vehicle, the switch
rate at the downstream sensor approaches that of the
upstream sensor. If at any point during the test
period the switch ratio reaches a predetermined
value, a counter is incremented by one. The monitor
is enabled to run another test during that trip. When
the test fails three times, the counter increments to
three, a malfunction is entered, and a Freeze Frame
is stored. When the counter increments to three dur­ing the next trip, the code is matured and the MIL is
illuminated. If the test passes the first, no further
testing is conducted during that trip.

The MIL is extinguished after three consecutive
good trips. The good trip criteria for the catalyst
monitor is more stringent than the failure criteria. In
order to pass the test and increment one good trip,
the downstream sensor switch rate must be less than
80% of the upstream rate (60% for manual transmis­sions). The failure percentages are 90% and 70%
respectively.

25 - 20 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

Enabling Conditions— The following conditions
must typically be met before the PCM runs the cat­alyst monitor. Specific times for each parameter may
be different from engine to engine.

• Accumulated drive time

• Enable time

• Ambient air temperature

• Barometric pressure

• Catalyst warm-up counter

• Engine coolant temperature

• Accumulated throttle position sensor

• Vehicle speed

• MAP

• RPM

• Engine in closed loop

• Fuel level

Pending Conditions—

• Misfire DTC

• Front Oxygen Sensor Response

• Front Oxygen Sensor Heater Monitor

• Front Oxygen Sensor Electrical

• Rear Oxygen Sensor Rationality (middle check)

• Rear Oxygen Sensor Heater Monitor

• Rear Oxygen Sensor Electrical

• Fuel System Monitor

• All TPS faults

• All MAP faults

• All ECT sensor faults

• Purge flow solenoid functionality

• Purge flow solenoid electrical

• All PCM self test faults

• All CMP and CKP sensor faults

• All injector and ignition electrical faults

• Idle Air Control (IAC) motor functionality

• Vehicle Speed Sensor

• Brake switch

• Intake air temperature

Conflict— The catalyst monitor does not run if
any of the following are conditions are present:

• EGR Monitor in progress

• Fuel system rich intrusive test in progress

• EVAP Monitor in progress

• Time since start is less than 60 seconds

• Low fuel level

• Low ambient air temperature

Suspend— The Task Manager does not mature a
catalyst fault if any of the following are present:

• Oxygen Sensor Monitor, Priority 1

• Upstream Oxygen Sensor Heater, Priority 1

• EGR Monitor, Priority 1

• EVAP Monitor, Priority 1

• Fuel System Monitor, Priority 2

• Misfire Monitor, Priority 2

NON-MONITORED CIRCUITS

OPERATION

The PCM does not monitor all circuits, systems
and conditions that could have malfunctions causing
driveability problems. However, problems with these
systems may cause the PCM to store diagnostic trou­ble codes for other systems or components. For exam­ple, a fuel pressure problem will not register a fault
directly, but could cause a rich/lean condition or mis­fire. This could cause the PCM to store an oxygen
sensor or misfire diagnostic trouble code.

The major non-monitored circuits are listed below
along with examples of failures modes that do not
directly cause the PCM to set a DTC, but for a sys­tem that is monitored.

FUEL PRESSURE

The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diag­nostic trouble code.

SECONDARY IGNITION CIRCUIT

The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.

CYLINDER COMPRESSION

The PCM cannot detect uneven, low, or high engine
cylinder compression.

EXHAUST SYSTEM

The PCM cannot detect a plugged, restricted or
leaking exhaust system. It may set a EGR or Fuel
system fault or O2S.

FUEL INJECTOR MECHANICAL MALFUNCTIONS

The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injector
is installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system.

EXCESSIVE OIL CONSUMPTION

Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.

THROTTLE BODY AIR FLOW

The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.

NS EMISSION CONTROL SYSTEMS 25 - 21

DESCRIPTION AND OPERATION (Continued)

VACUUM ASSIST

The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.

PCM SYSTEM GROUND

The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod­ule should be mounted to the body at all times, also
during diagnostic.

PCM CONNECTOR ENGAGEMENT

The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connec­tor pins.

SPECIFICATIONS

LOAD VALUE

HIGH AND LOW LIMITS

OPERATION

The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos­tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.

ENGINE IDLE/NEUTRAL 2500 RPM/NEUTRAL

2.4 Auto. Trans. 4.4% of Maximun Load 11.7% of Maximun Load

3.0L 4.2% of Maximun Load 11.5% of Maximun Load

3.3L 5% of Maximun Load 13.4% of Maximun Load

3.8L 4.7% of Maximun Load 13.3% of Maximun Load

25 - 22 EMISSION CONTROL SYSTEMS NS

EVAPORATIVE EMISSION CONTROLS

TABLE OF CONTENTS

page page

DESCRIPTION AND OPERATION

EVAPORATION CONTROL SYSTEM ..........22

EVAPORATIVE (EVAP) CANISTER............22

PROPORTIONAL PURGE SOLENOID .........23

LEAK DETECTION PUMP ..................23

LEAK DETECTION PUMP PRESSURE

SWITCH ..............................23

POSITIVE CRANKCASE VENTILATION (PCV)

SYSTEMS.............................24

DESCRIPTION AND OPERATION

EVAPORATION CONTROL SYSTEM

OPERATION

The evaporation control system prevents the emis­sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to an activated carbon
filled evaporative canister. The canister temporarily
holds the vapors. The Powertrain Control Module
(PCM) allows intake manifold vacuum to draw
vapors into the combustion chambers during certain
operating conditions.

All engines use a proportional purge system. The
PCM controls vapor flow by operating the purge sole­noid. Refer to Proportional Purge Solenoid in this
section.

POSITIVE CRANKCASE VENTILATION VALVE. . . 25

CRANKCASE VENT FILTER.................26

VEHICLE EMISSION CONTROL

INFORMATION LABEL ...................26

REMOVAL AND INSTALLATION

LEAK DETECTION PUMP REPLACEMENT .....26

NOTE: The evaporative system uses specially man­ufactured hoses. If they need replacement, only use
fuel resistant hose.

NOTE: For more information on Onboard Refueling
Vapor Recovery (ORVR), refer to the Fuel Delivery
section.

EVAPORATIVE (EVAP) CANISTER

DESCRIPTION

The canister is attached to the frame under the
driver’s seat (Fig. 1).

OPERATION

All vehicles use a sealed, maintenance free, evapo­rative (charcoal) canister.

Fig. 1 Evaporative Canister

1 – FUEL TANK VENT
2 – PURGE HOSE
3 – PRESSURE HOSE FROM LEAK DETECTION PUMP
4 – EVAPORATIVE CANISTER

Fuel tank vapor vents into the canister. The canis­ter temporarily holds the fuel vapors until intake
manifold vacuum draws them into the combustion
chamber. The canister proportional purge solenoid
allows the canister to be purged at predetermined
intervals and engine conditions.

NS EMISSION CONTROL SYSTEMS 25 - 23

DESCRIPTION AND OPERATION (Continued)

PROPORTIONAL PURGE SOLENOID

DESCRIPTION

Fig. 2 Proportional Purge Solenoid

1 – PROPORTIONAL PURGE SOLENOID

OPERATION

All vehicles use a proportional purge solenoid. The
solenoid regulates the rate of vapor flow from the
EVAP canister to the throttle body. The PCM oper­ates the solenoid.

During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole­noid. When de-energized, no vapors are purged.

The proportional purge solenoid operates at a fre­quency of 200 hz and is controlled by an engine con­troller circuit that senses the current being applied
to the proportional purge solenoid and then adjusts
that current to achieve the desired purge flow. The
proportional purge solenoid controls the purge rate of
fuel vapors from the vapor canister and fuel tank to
the engine intake manifold.

LEAK DETECTION PUMP

DESCRIPTION

The leak detection pump is a device used to detect
a leak in the evaporative system.

The pump contains a 3 port solenoid, a pump that
contains a switch, a spring loaded canister vent valve
seal, 2 check valves and a spring/diaphragm.

OPERATION

Immediately after a cold start, when the engine
temperature is between 40°F and 86°F, the 3 port
solenoid is briefly energized. This initializes the

pump by drawing air into the pump cavity and also
closes the vent seal. During non-test test conditions,
the vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi­tion. The vent seal will remain closed while the
pump is cycling. This is due to the operation of the 3
port solenoid which prevents the diaphragm assem­bly from reaching full travel. After the brief initial­ization period, the solenoid is de-energized, allowing
atmospheric pressure to enter the pump cavity. This
permits the spring to drive the diaphragm which
forces air out of the pump cavity and into the vent
system. When the solenoid is energized and de-ener­gized, the cycle is repeated creating flow in typical
diaphragm pump fashion. The pump is controlled in
2 modes:

PUMP MODE: The pump is cycled at a fixed rate
to achieve a rapid pressure build in order to shorten
the overall test time.

TEST MODE: The solenoid is energized with a
fixed duration pulse. Subsequent fixed pulses occur
when the diaphragm reaches the switch closure
point.

The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5 inches
of water.

When the pump starts, the cycle rate is quite high.
As the system becomes pressurized, pump rate drops.
If there is no leak, the pump will quit. If there is a
leak, the test is terminated at the end of the test
mode.

If there is no leak, the purge monitor is run. If the
cycle rate increases due to the flow through the
purge system, the test is passed and the diagnostic is
complete.

The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.

LEAK DETECTION PUMP PRESSURE SWITCH

DESCRIPTION

The primary components within the leak detection
pump assembly are: a three-port leak detection sole­noid valve, a pump assembly that includes a spring
loaded diaphragm, a reed switch which is used to
monitor the pump diaphragm movement (position),
two check valves, and a spring loaded vent seal
valve.

OPERATION

The leak detection pump LDP assembly incorpo­rates two primary functions: it detects a leak in the
evaporative system, and it seals the evaporative sys­tem so that the required leak detection monitor test
can be run.

25 - 24 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

The three-port LDP solenoid valve is used to
expose either engine vacuum or atmospheric pressure
to the top side of the leak detection pump diaphragm.

When the LDP solenoid valve is deenergized its
port (opening) to engine vacuum is blocked off. This
allows ambient air (atmospheric pressure) to enter
the top of the pump diaphragm. The spring load on
the diaphragm will push the diaphragm down, as
long as there is no pressure present in the rest of the
evaporative system. If there is sufficient evaporative
system pressure present, then the pump diaphragm
will stay in the “up” position. If the evaporative sys­tem pressure decays, then the pump diaphragm will
eventually fall. The rate of this decent is dependent
upon the size of the evaporative system leak (Large
or small).

When the LDP solenoid valve is energized the port
(opening) to atmosphere is blocked off. At the same
time, the port to engine vacuum is opened. Engine
vacuum replaces atmospheric pressure. When engine
vacuum is sufficient, it over comes the spring pres­sure load on the pump diaphragm and causes the
diaphragm to rise to its “up” position. The reed
switch will change state depending upon the position
of the pump diaphragm.

If the diaphragm is in the “up” position the reed
switch will be in its “open” state. This means that
the 12 volt signal sense to the PCM is interrupted.
Zero volts is detected by the PCM. If the pump dia­phragm is in the “down” position the reed switch will
be in its “closed” state. 12 volts is sent to the PCM
via the switch sense circuit.

The check valves are one-way valves. The first
check valve is used to draw outside air into the lower
chamber of the LDP (the space that is below the
pump diaphragm). The second check valve is used to
vent this outside air, which has become pressurized
from the fall of the pump diaphragm, into the evap­orative system.

The spring loaded vent seal valve, inside the LDP
is used to seal off the evaporative system. When the
pump diaphragm is in the “up” position the spring
pushes the vent seal valve closed. The vent seal valve
opens only when the pump diaphragm is in its “full
down” position. When the pump assembly is in its
pump mode the pump diaphragm is not allowed to
descend (fall) so far as to allow the vent seal valve to
open. This allows the leak detection pump to develop
the required pressure within the evaporative system
for system leak testing.

A pressure build up within the evaporative system
may cause pressure on the lower side of the LDP dia­phragm. This will cause the LDP diaphragm to
remain in its “up” position (stuck in the up position).
This condition can occur even when the solenoid
valve is deenergized. This condition can be caused by

previous cycling (pumping) of the LDP by the techni­cian (dealer test). Another way that this condition is
created is immediately following the running of the
vehicle evaporative system monitor. In this case, the
PCM has not yet opened the proportional purge sole­noid in order to vent the pressure that has been built
up in the evaporative system to the engine combus­tion system. The technician will need to vent the
evaporative system pressure via the vehicle fuel filler
cap and its fuel filler secondary seal (if so equipped
in the fuel filler neck). This will allow the technician
to cycle the LDP and to watch switch state changes.

After passing the leak detection phase of the test,
system pressure is maintained until the purge sys­tem is activated, in effect creating a leak. If the dia­phragm falls (as is expected), causing the reed switch
to change state, then the diagnostic test is completed.

When of the evaporative system leak monitor
begins its various tests, a test is performed to deter­mine that no part of the evaporative system is
blocked. In this test, the LDP is cycled (pumped) a
calibrated (few) number of times. Pressure should not
build up in the evaporative system. If pressure is
present, then LDP diaphragm is forced to stay in its
“up” position. The reed switch now stays open and
the PCM senses this open (incorrect) state. The evap­orative system monitor will fail the test because of a
detected obstruction within the system.

Possible causes:

• Open or shorted LDP switch sense circuit

• Leak Detection Pump switch failure

• Open fused ignition switch output

• Restricted, disconnected, or blocked manifold

vacuum source

• Obstruction of hoses or lines

• PCM failure

POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEMS

DESCRIPTION
OPERATION

Intake manifold vacuum removes crankcase vapors
and piston blow-by from the engine. The vapors pass
through the PCV valve into the intake manifold
where they become part of the calibrated air-fuel
mixture. They are burned and expelled with the
exhaust gases. The air cleaner supplies make up air
when the engine does not have enough vapor or
blow-by gases. In this system, fresh filtered air
enters the crankcase (Fig. 3), (Fig. 4) and (Fig. 5).

NS EMISSION CONTROL SYSTEMS 25 - 25

DESCRIPTION AND OPERATION (Continued)

Fig. 3 PCV Valve—2.4L Engine

1 – PCV VALVE
2 – INTAKE MANIFOLD

Fig. 4 PCV Valve —3.0L Engine

1 – PCV HOSE
2 – POSITIVE CRANKCASE VENTILATION (PCV) VALVE
3 – VALVE COVER

POSITIVE CRANKCASE VENTILATION VALVE

OPERATION

The PCV valve contains a spring loaded plunger.
The plunger meters the amount of crankcase vapors
routed into the combustion chamber based on intake
manifold vacuum.

When the engine is not operating or during an
engine backfire, the spring forces the plunger back
against the seat. This prevents vapors from flowing
through the valve (Fig. 6).

When the engine is at idle or cruising, high manifold
vacuum is present. At these times manifold vacuum is
able to completely compress the spring and pull the
plunger to the top of the valve (Fig. 7). In this position
there is minimal vapor flow through the valve.

Fig. 5 PCV Valve and Fresh Air Hose— 3.3/3.8L

Engines

1 – THROTTLE BODY
2 – RESONATOR
3 – FRESH AIR HOSE
4 – PCV VALVE

Fig. 6 Engine Off or Engine Backfire—No Vapor

Flow

Fig. 7 High Intake Manifold Vacuum—Minimal Vapor

Flow

During periods of moderate intake manifold vac­uum the plunger is only pulled part way back from
the inlet. This results in maximum vapor flow
through the valve (Fig. 8).

25 - 26 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

Fig. 8 Moderate Intake Manifold Vacuum—Maximum

Vapor Flow

CRANKCASE VENT FILTER

OPERATION

All engines use filtered air to vent the crankcase.
The filtered air is drawn through the resonator
assembly located between the air cleaner and throttle
body.

VEHICLE EMISSION CONTROL INFORMATION
LABEL

DESCRIPTION

All models have a Vehicle Emission Control Infor­mation (VECI) Label. Chrysler permanently attaches
the label in the engine compartment. It cannot be
removed without defacing information and destroying
the label.

The label contains the vehicle’s emission specifica­tions and vacuum hose routings. All hoses must be
connected and routed according to the label.

REMOVAL AND INSTALLATION

LEAK DETECTION PUMP REPLACEMENT

REMOVAL

The Leak Detection Pump (LDP) is located under
the driver’s side in the cast cradle under the steering
gear (Fig. 9).

(1) Raise and support vehicle on a hoist.

(2) Push locking tab on connector to unlock (Fig.

10).

(3) Push down on connector latch and pull connec­tor from pump.

(4) Remove hoses.

Remove bolts holding LDP and bracket to cradle.

(5)

(6) Remove bracket from LDP.

Fig. 9 Leak Detection Pump

Fig. 10 Leak Detection Pump Connector Lock

1 – ELECTRICAL CONNECTOR
2 – MOUNTING BOLTS

INSTALLATION

(1) Install LDP to bracket.

(2) Install LDP and bracket to cradle. Torque bolts
to 9.5-14 N·m (85-125 in. lbs.). Before installing

hoses to LDP, make sure they are not cracked
or split. If a hose leaks, it will cause the Check
Engine Lamp to illuminate.

(3) Install hoses to LDP.
(4) Plug electrical connector into LDP.
(5) Push connector locking tab into place.
(6) Lower vehicle
(7) Using DRB scan tool, verify proper operation of

LDP.

NS EMISSION CONTROL SYSTEMS 25 - 27

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

TABLE OF CONTENTS

page page

DESCRIPTION AND OPERATION

EXHAUST GAS RECIRCULATION ............27

REMOVAL AND INSTALLATION

EGR VALVE SERVICE—3.0L ENGINES ........28

EGR VALVE SERVICE—3.3/3.8L ENGINES .....29

DESCRIPTION AND OPERATION

EXHAUST GAS RECIRCULATION

DESCRIPTION

The EGR system consists of:

• EGR tube (connects a passage in the intake

manifold to the exhaust manifold)

• EGR valve

• Electronic EGR Transducer

• Connecting hoses

EGR TUBE SERVICE—3.0L ENGINES .........29

EGR TUBE SERVICE—3.3/3.8L ENGINES ......29

SPECIAL TOOLS

EMISSION CONTROL SYSTEM ..............30

Fig. 2 EGR Mounting—3.0L Engine

1 – EGR SOLENOID
2 – EGR VALVE
3 – EGR TUBE
4 – TRANSDUCER

Fig. 1 EGR Mounting—2.4L Engine

1 – EGR SOLENOID AND TRANSDUCER
2 – EGR VALVE
3 – EGR TUBE

OPERATION

Refer to Monitored Systems - EGR Monitor in this
group for more information.

The engines use Exhaust Gas Recirculation (EGR)
systems (Fig. 1), (Fig. 2) and (Fig. 3). The EGR sys­tem reduces oxides of nitrogen (NOx) in engine
exhaust and helps prevent detonation (engine knock).
Under normal operating conditions, engine cylinder

temperature can reach more than 3000°F. Formation
of NOx increases proportionally with combustion
temperature. To reduce the emission of these oxides,
the cylinder temperature must be lowered. The sys­tem allows a predetermined amount of hot exhaust
gas to recirculate and dilute the incoming air/fuel
mixture. The diluted air/fuel mixture reduces peak
flame temperature during combustion.

The electric EGR transducer contains an electri­cally operated solenoid and a back-pressure trans­ducer (Fig. 4). The Powertrain Control Module (PCM)
operates the solenoid. The PCM determines when to
energize the solenoid. Exhaust system back-pressure
controls the transducer.

When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to the
transducer when the PCM de-energizes the solenoid.

When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the trans­ducer. When the PCM de-energizes the solenoid and
back-pressure closes the transducer bleed valve, vac-

25 - 28 EMISSION CONTROL SYSTEMS NS

DESCRIPTION AND OPERATION (Continued)

Fig. 3 EGR Mounting—3.3/3.8L Engines

1 – BACKPRESSURE TRANSDUCER
2 – EGR SOLENOID
3 – EGR VALVE

uum flows through the transducer to operate the
EGR valve.

De-energizing the solenoid, but not fully closing the
transducer bleed hole (because of low back-pressure),
varies the strength of vacuum applied to the EGR
valve. Varying the strength of the vacuum changes
the amount of EGR supplied to the engine. This pro­vides the correct amount of exhaust gas recirculation
for different operating conditions.

This system does not allow EGR at idle.

A failed or malfunctioning EGR system can cause
engine spark knock, sags or hesitation, rough idle,
engine stalling and increased emissions.

REMOVAL AND INSTALLATION

EGR VALVE SERVICE—3.0L ENGINES

The EGR valve and Electrical EGR Transducer are
serviced as an assembly.

Fig. 4 Electric EGR Transducer

1 – DIAPHRAGM
2 – PISTON
3 – SPRING
4 – EGR VALVE ASSEMBLY
5 – VACUUM MOTOR
6 – VACUUM MOTOR FITTING
7 – VACUUM OUTLET FITTING TO EGR VALVE
8 – EGR VALVE CONTROL ASSEMBLY
9 – ELECTRIC SOLENOID PORTION OF VALVE CONTROL
10 – VACUUM INLET FITTING FROM ENGINE
11 – BACK-PRESSURE HOSE
12 – TRANSDUCER PORTION OF VALVE CONTROL
13 – ELECTRICAL CONNECTION POINT
14 – EGR VALVE BACK-PRESSURE FITTING
15 – EXHAUST GAS INLET
16 – STEM PROTECTOR AND BUSHING
17 – BASE
18 – MOVEMENT INDICATOR
19 – POPPET VALVE
20 – SEAT
21 – EXHAUST GAS OUTLET

REMOVAL

(1) Disconnect the electric and vacuum connectors
from the electric EGR transducer (Fig. 5).

(2) Remove EGR valve mounting bolts.

(3) Clean all gasket surfaces and discard old gas­kets. Check for any signs of leakage or cracked sur­faces. Repair or replace as necessary.

INSTALLATION

(1) Install EGR valve and new gasket on intake
manifold. Tighten mounting bolts to 22 N·m (200 in.
lbs.) torque.

(2) Connect the electrical and vacuum connectors
to the electric EGR transducer.

NS EMISSION CONTROL SYSTEMS 25 - 29

REMOVAL AND INSTALLATION (Continued)

Fig. 5 EGR System Service—3.0L Engines

1 – ELECTRICAL EGR TRANSDUCER
2 – EGR VALVE
3 – EGR TUBE
4 – EXHAUST MANIFOLD
5 – INTAKE MANIFOLD

EGR VALVE SERVICE—3.3/3.8L ENGINES

The EGR valve and Electrical EGR Transducer are

serviced as an assembly.

REMOVAL

(1) Disconnect vacuum tube from electric EGR

transducer. Inspect vacuum tube for damage (Fig. 6).

(2) Remove electrical connector from solenoid.
(3) Remove EGR valve bolts from intake manifold.
(4) Open EGR transducer clip and remove electric

EGR transducer.

(5) Remove EGR valve from intake manifold.

(6) Clean gasket surface and discard old gasket.
Check for any signs of leakage or cracked surfaces.
Repair or replace as necessary.

INSTALLATION

(1) Assemble EGR valve with new gasket onto the
intake manifold.

(2) Install mounting bolts. Tighten bolts to 22 N·m
(200 in. lbs.) torque.

(3) Install electric EGR transducer in clip with ori­entation tab in slot and snap closed.

(4) Reconnect vacuum hose and electrical connec­tor to electrical EGR transducer.

Fig. 6 EGR System—3.3/3.8L Engines

1 – BACKPRESSURE TRANSDUCER
2 – EGR SOLENOID
3 – EGR VALVE

EGR TUBE SERVICE—3.0L ENGINES

REMOVAL

(1) Remove EGR tube flange nuts from exhaust

manifold (Fig. 5).

(2) Remove EGR valve nuts at intake manifold.

Remove EGR tube.

(3) Clean all gasket surfaces and discard old gas­kets. Check for any signs of leakage or cracked sur­faces. Repair or replace as necessary.

INSTALLATION

(1) Loosely install the EGR tube on the intake and
exhaust manifolds with new gaskets.

(2) Tighten EGR tube flange bolts at the intake
manifold to 22 N·m (200 in. lbs.) torque.

(3) Tighten EGR tube to exhaust manifold nuts to
22 N·m (200 in. lbs.) torque.

EGR TUBE SERVICE—3.3/3.8L ENGINES

REMOVAL

(1) Remove EGR tube attaching bolts from intake
and exhaust manifolds (Fig. 7).

(2) Clean intake and exhaust manifold gasket sur­faces. Discard old gasket.

(3) Check for signs of leakage or cracked surfaces
on either manifolds or tube. Repair or replace as nec­essary.

25 - 30 EMISSION CONTROL SYSTEMS NS

REMOVAL AND INSTALLATION (Continued)

INSTALLATION

(1) Loosely assemble EGR tube and new gaskets
into place on intake and exhaust manifolds.

(2) Tighten mounting bolts to 22 N·m (200 in. lbs.)
torque.

SPECIAL TOOLS

EMISSION CONTROL SYSTEM

Fig. 7 EGR Tube—3.3/3.8L

1 – EET TRANSDUCER
2 – OXYGEN SENSOR
3 – EGR TUBE
4 – EGR VALVE

Hose Clamp Pliers 6094