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EXJ_25
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Datasheet exj_25 Datasheet

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Page 1
XJ EMISSION CONTROL SYSTEMS 25 - 1
EMISSION CONTROL SYSTEMS
TABLE OF CONTENTS
page page
ON-BOARD DIAGNOSTICS ................... 1 EVAPORATIVE EMISSION CONTROLS ......... 23

ON-BOARD DIAGNOSTICS

TABLE OF CONTENTS
page page

DESCRIPTION AND OPERATION

EMISSION SYSTEM........................1
STATE DISPLAY TEST MODE ................2
CIRCUIT ACTUATION TEST MODE ............2
DIAGNOSTIC TROUBLE CODES ..............2
DIAGNOSTIC TROUBLE CODE
DESCRIPTIONS .........................3
DESCRIPTION AND OPERATION

EMISSION SYSTEM

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 warm-up cycles. Diagnostic trouble codes that affect vehicle emissions illuminate the Malfunction Indicator Lamp (MIL). The MIL is displayed as an engine icon on the instrument panel. Refer to Malfunction Indicator Lamp (MIL) 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
TASK MANAGER .........................16
MONITORED SYSTEMS....................19
TRIP DEFINITION ........................21
COMPONENT MONITORS ..................21
NON-MONITORED CIRCUITS ...............22
HIGH AND LOW LIMITS....................22
LOAD VALUE............................22
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 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.
Technicians must retrieve stored DTC’s by connect­ing the DRB scan tool (or an equivalent scan tool) to the 16–way data link connector (Fig. 1).
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, connect the DRB scan tool to the 16–way data link connector to erase all DTC’s and extinguish the MIL.
Page 2
25 - 2 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
10 % of the load of the operating condition at which the malfunction was first detected.

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. Connect the DRB scan tool to the data link connector and access the state display screen. Then access either State Display Inputs and Outputs or State Display Sensors.
Fig. 1 Data Link (Diagnostic) Connector Location
1 – 16–WAY DATALINK CONNECTOR

MALFUNCTION INDICATOR LAMP (MIL)

DESCRIPTION
The Malfunction Indicator Lamp (MIL) is located on the instrument panel. It is displayed as an engine icon (graphic).
OPERATION
As a functional test, the 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 to the instrument cluster to illumi­nate the lamp. The PCM illuminates the MIL only for DTC’s that affect vehicle emissions. There are some monitors that may take two consecutive trips, with a detected fault, before the MIL is illuminated. The MIL stays on continuously when the PCM has entered a Limp-In mode or identified a failed emis­sion component. 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

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. Connect the DRB scan tool to the data link connector and access the Actuators screen.

DIAGNOSTIC TROUBLE CODES

OPERATION
A Diagnostic Trouble Code (DTC) indicates that the Powertrain Control Module (PCM) has recognized an abnormal condition in the system.
DTC’s are the results of a system or circuit failure, but do not directly identify the failed component or components.
Technicians must retrieve stored DTC’s by connect­ing the DRB III scan tool (or an equivalent scan tool) to the 16–way data link connector. This connector is located on the lower edge of the instrument panel near the steering column.
OBTAINING DTC’s
WARNING: APPLY PARKING BRAKE AND/OR BLOCK WHEELS BEFORE PERFORMING ANY TEST ON AN OPERATING ENGINE.
Page 3
XJ EMISSION CONTROL SYSTEMS 25 - 3
DESCRIPTION AND OPERATION (Continued)
(1) Connect the DRB scan tool to data link (diag-
nostic) connector.
(2) Turn the ignition switch on, access Read Fault Screen. Record all the DTC’s shown on the DRB scan tool.
(3) To erase DTC’s, use the Erase Trouble Code
data screen on the DRB scan tool.
NOTE: For a list of DTC’s, refer to the following charts.

DIAGNOSTIC TROUBLE CODE DESCRIPTIONS

(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
(G) Generator lamp illuminated
Generic Scan
Tool P-Code
P0030 (M) 1/1 O2 Sensor Heater Relay Circuit Problem detected in oxygen sensor heater relay circuit. P0036 (M) 1/2 O2 Sensor Heater Relay Circuit Problem detected in oxygen sensor heater relay circuit.
P0106 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
P0121 (M) Accelerator Position Sensor (APPS)
P0122 (M) Throttle Position Sensor Voltage Low Throttle position sensor input below the acceptable
P0122 (M) Accelerator Position Sensor (APPS)
P0123 (M) Throttle Position Sensor Voltage
P0123 (M) Accelerator Position Sensor (APPS)
P0125 (M) Closed Loop Temp Not Reached Time to enter Closed Loop Operation (Fuel Control) is
P0125 (M) Engine is Cold Too Long Engine does not reach operating temperature. P0130 (M) 1/1 O2 Sensor Heater Circuit
DRB Scan Tool Display Brief Description of DTC
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
APPS voltage input below the minimum acceptable
Signal Voltage Too Low
APPS voltage input below the minimum acceptable
Signal Voltage Too Low
Throttle position sensor input above the maximum
High
APPS voltage input above the maximum acceptable
Signal Voltage Too High
Oxygen sensor heater element malfunction.
Malfunction
voltage.
voltage range.
voltage.
acceptable voltage.
voltage.
excessive.
Page 4
25 - 4 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0131 (M) 1/1 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal
operating range.
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 (M) 1/2 O2 Sensor Heater Circuit
Malfunction
P0137 (M) 1/2 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal
P0138 (M) 1/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal
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
P0141 (M) 1/2 O2 Sensor Heater Failure Oxygen sensor heater element malfunction. P0143 (M) 1/3 O2 Sensor Shorted To Ground Oxygen sensor input voltage maintained below normal
P0144 (M) 1/3 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal
P0145 (M) 1/3 O2 Sensor Slow Response Oxygen sensor response slower than minimum required
P0146 (M) 1/3 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen
P0147 (M) 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
P0152 (M) 2/1 O2 Sensor Shorted To Voltage Oxygen sensor input voltage sustained above normal
P0153 (M) 2/1 O2 Sensor Slow Response Oxygen sensor response slower than minimum required
P0154 (M) 2/1 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen
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
P0158 (M) 2/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal
P0159 2/2 O2 Sensor Slow Response Oxygen sensor response slower than minimum required
P0160 (M) 2/2 O2 Sensor Stays at Center Neither rich or lean condition is detected from the oxygen
Oxygen sensor heater element malfunction.
operating range.
operating range.
sensor.
operating range.
operating range.
switching frequency.
sensor.
operating range.
operating range.
switching frequency.
sensor.
operating range.
operating range.
switching frequency.
sensor.
Page 5
XJ EMISSION CONTROL SYSTEMS 25 - 5
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0161 (M) 2/2 O2 Sensor Heater Failure Oxygen sensor heater element malfunction.
P0168 Decreased Engine Performance Due
To High Injection Pump Fuel Temp
P0171 (M) 1/1 Fuel System Lean A lean air/fuel mixture has been indicated by an
P0172 (M) 1/1 Fuel System Rich A rich air/fuel mixture has been indicated by an
P0174 (M) 2/1 Fuel System Lean A lean air/fuel mixture has been indicated by an
P0175 (M) 2/1 Fuel System Rich A rich air/fuel mixture has been indicated by an
P0176 Loss of Flex Fuel Calibration Signal No calibration voltage present from flex fuel sensor. P0177 Water In Fuel Excess water found in fuel by water-in-fuel sensor. P0178 Flex Fuel Sensor Volts Too Low Flex fuel sensor input below minimum acceptable voltage. P0178 Water In Fuel Sensor Voltage Too
Low
P0179 Flex Fuel Sensor Volts Too High Flex fuel sensor input above maximum acceptable
P0181 Fuel Injection Pump Failure Low power, engine derated, or engine stops.
P0182 (M) CNG Temp Sensor Voltage Too Low Compressed natural gas temperature sensor voltage
P0183 (M) 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 (M) Injector #7 Control Circuit Injector #7 output driver stage does not respond properly
P0208 (M) Injector #8 Control Circuit Injector #8 output driver stage does not respond properly
P0209 (M) Injector #9 Control Circuit Injector #9 output driver stage does not respond properly
P0210 (M) Injector #10 Control Circuit Injector #10 output driver stage does not respond properly
P0215 Fuel Injection Pump Control Circuit Failure in fuel pump relay control circuit.
Fuel temperature is above the engine protection limit.
Engine power will be derated.
abnormally rich correction factor.
abnormally lean correction factor.
abnormally rich correction factor.
abnormally lean correction factor.
Loss of water-in-fuel circuit or sensor.
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.
Page 6
25 - 6 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0216 (M) Fuel Injection Pump Timing Failure High fuel supply restriction, low fuel pressure or possible
wrong or incorrectly installed pump keyway.
P0217 Decreased Engine Performance Due
To Engine Overheat Condition
P0219 Crankshaft Position Sensor
Overspeed Signal P0222 (M) Idle Validation Signals Both Low Problem detected with idle validation circuits within APPS. P0223 (M) Idle Validation Signals Both High
(Above 5 Volts)
P0230 Transfer Pump (Lift Pump) Circuit
Out of Range
P0232 Fuel Shutoff Signal Voltage Too High Fuel shut-off signal voltage too high from ECM to fuel
P0234 (M) Turbo Boost Limit Exceeded Problem detected in turbocharger wastegate. P0236 (M) Map Sensor Too High Too Long Problem detected in turbocharger wastegate. P0237 (M) Map Sensor Voltage Too Low MAP sensor voltage input below the minimum acceptable
P0238 (M) Map Sensor Voltage Too High MAP sensor voltage input above the maximum
P0251 (M) Fuel Inj. Pump Mech. Failure Fuel
Valve Feedback Circuit
P0253 (M) Fuel Injection Pump Fuel Valve
Open Circuit
P0254 Fuel Injection Pump Fuel Valve
Current Too High 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. 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 (M) No Crank Referance Signal at PCM No reference signal (crankshaft position sensor) detected
P0320 (M) No RPM Signal to PCM (Crankshaft
Position Sensor Signal to JTEC)
P0325 Knock Sensor #1 Circuit Knock sensor (#1) signal above or below minimum
Engine overheating. ECM will derate engine performance.
Engine has exceeded rpm limits.
Problem detected with idle validation circuits within APPS.
Problem detected in fuel transfer pump circuits.
injection pump.
voltage.
acceptable voltage.
Problem sensed with fuel circuit internal to fuel injection
pump.
Problem sensed with fuel circuit internal to fuel injection
pump.
Problem caused by internal fuel injection pump failure.
during engine cranking.
A CKP signal has not been detected at the PCM.
acceptable threshold voltage at particular engine speeds.
Page 7
XJ EMISSION CONTROL SYSTEMS 25 - 7
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0330 Knock Sensor #2 Circuit Knock sensor (#2) signal above or below minimum
acceptable threshold voltage at particular engine speeds.
P0336 (M) Crankshaft Position (CKP) Sensor
Signal P0340 (M) No Cam Signal At PCM No fuel sync P0341 (M) Camshaft Position (CMP) Sensor
Signal
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 (M) Ignition Coil # 7 Primary Circuit Peak primary circuit current not achieved with maximum
P0358 (M) Ignition Coil # 8 Primary Circuit Peak primary circuit current not achieved with maximum
P0370 Fuel Injection Pump Speed/Position
Sensor Sig Lost
P0380 (M) Intake Air Heater Relay #1 Control
Circuit P0381 (M) Wait To Start Lamp Inoperative Problem detected in wait-to-start bulb circuit. P0382 (M) Intake Air Heater Relay #2 Control
Circuit
P0387 Crankshaft Position Sensor Supply
Voltage Too Low
P0388 Crankshaft Position Sensor Supply
Voltage Too High
P0401 EGR System Failure Required change in air/fuel ration not detected during
P0403 EGR Solenoid Circuit An open or shorted condition detected in the EGR
P0404 EGR Position Sensor Rationality EGR position sensor signal does not correlate to EGR
P0405 EGR Position Sensor Volts Too Low EGR position sensor input below the acceptable voltage
Problem caused by internal fuel injection pump failure.
Problem detected in #1 air heater solenoid/relay circuit
Problem detected in #2 air heater solenoid/relay circuit
CKP sensor voltage input below the minimum acceptable
CKP sensor voltage input above the maximum acceptable
Problem with voltage signal from CKP.
Problem with voltage signal from CMP.
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).
(not heater element)
(not heater element)
voltage.
voltage.
diagnostic test.
solenoid control circuit.
duty cycle.
range.
Page 8
25 - 8 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0406 EGR Position Sensor Volts Too High EGR position sensor input above the acceptable voltage
range.
P0412 Secondary Air Solenoid Circuit An open or shorted condition detected in the secondary
air (air switching/aspirator) solenoid control circuit. 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
evaporative emission system operation.
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 (M) Evap Leak Monitor Small Leak
Detected
P0460 Fuel Level Unit No Change Over
Miles
P0460 Fuel Level Unit No Change Over
Miles
P0462 Fuel Level Sending Unit Volts Too
Low
P0462 (M) Fuel Level Sending Unit Volts Too
Low
P0463 Fuel Level Sending Unit Volts Too
High
P0463 (M) Fuel Level Sending Unit Volts Too
High
P0500 (M) No Vehicle Speed Sensor Signal No vehicle speed sensor signal detected during road load
P0500 (M) No Vehicle Speed Sensor Signal A vehicle speed signal was not detected. P0505 (M) Idle Air Control Motor Circuits SBEC II
P0522 Oil Pressure Voltage Too Low Oil pressure sending unit (sensor) voltage input below the
P0523 Oil Pressure Voltage Too High Oil pressure sending unit (sensor) voltage input above the
P0524 Oil Pressure Too Low Engine oil pressure is low. Engine power derated. P0545 A/C Clutch Relay Circuit Problem detected in air conditioning clutch relay control
P0551 Power Steering Switch Failure Incorrect input state detected for the power steering
P0562 Charging System Voltage Too Low Supply voltage sensed at ECM too low. P0563 Charging System Voltage Too High Supply voltage sensed at ECM too high.
A small leak has been detected in the evaporative
system.
solenoid control circuit.
A large leak has been detected in the evaporative system.
Leak has been detected in the evaporative system.
During low fuel
Fuel level sending unit voltage does not change for more
than 40 miles.
Fuel level sensor input below acceptable voltage.
Open circuit between PCM and fuel gauge sending unit.
Fuel level sensor input above acceptable voltage.
Circuit shorted to voltage between PCM and fuel gauge
sending unit.
conditions.
minimum acceptable voltage.
maximum acceptable voltage.
circuit.
switch circuit. PL: High pressure seen at high speed.
Page 9
XJ EMISSION CONTROL SYSTEMS 25 - 9
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0600 PCM Failure SPI Communications No communication detected between co-processors in the
control module.
P0601 (M) Internal Controller Failure Internal control module fault condition (check sum)
detected.
P0602 (M) ECM Fueling Calibration Error ECM Internal fault condition detected.
P0604 RAM Check Failure Transmission control module RAM self test fault detected.
-Aisin transmission
P0605 ROM Check Falure Transmission control module ROM self test fault detected
-Aisin transmission
P0606 (M) ECM Failure ECM Internal fault condition detected.
P0615 Starter Relay Control Circuit An open or shorted condition detected in the starter relay
control circuit.
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 EATX Controller DTC Present This SBEC III or JTEC DTC indicates that the EATX or
P0703 Brake Switch Stuck Pressed or
Released
P0711 (M) Trans Temp Sensor, No Temp Rise
After Start
P0712 Trans Temp Sensor Voltage Too Low Transmission fluid temperature sensor input below
P0712 (M) Trans Temp Sensor Voltage Too Low Voltage less than 1.55 volts (4-speed auto. trans. only).
P0713 Trans Temp Sensor Voltage Too
High
P0713 (M) Trans Temp Sensor Voltage Too
High
P0720 (M) Low Output SPD Sensor RPM,
Above 15 MPH
P0720 (M) Low Output Spd Sensor RPM Above
15 mph
P0740 (M) Torq Con Clu, No RPM Drop at
Lockup
P0743 (M) Torque Converter Clutch Solenoid/
Trans Relay Circuits
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. Was MIL code 37.
acceptable voltage. Was MIL code 37.
Transmission fluid temperature sensor input above
acceptable voltage. Was MIL code 37.
Voltage greater than 3.76 volts (4-speed auto. trans.
only).
The relationship between the Output Shaft Speed Sensor
and vehicle speed is not within acceptable limits.
Output shaft speed is less than 60 rpm with vehicle speed
above 15 mph (4-speed auto. trans. only).
Relationship between engine and vehicle speeds
indicated failure of torque convertor clutch lock-up system
(TCC/PTU solenoid)
An open or shorted condition detected in the torque
converter clutch (part throttle unlock) solenoid control
circuit. Shift solenoid C electrical fault - Aisin transmission
Page 10
25 - 10 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P0743 (M) Torque Converter Clutch Solenoid/
Trans Relay Circuits
P0748 (M) Governor Pressur Sol Control/Trans
Relay Circuits
P0748 (M) Governor Pressure Sol Control/Trans
Relay Circuits
P0751 (M) O/D Switch Pressed (Lo) More Than
5 Minutes
P0751 (M) O/D Switch Pressed (LO) More Than
5 Min
P0753 (M) Trans 3-4 Shift Sol/Trans Relay
Circuits
P0753 (M) Trans 3-4 Shift Sol/Trans Relay
Circuits
P0756 AW4 Shift Sol B (2-3) Functional
Failure
P0783 (M) 3-4 Shift Sol, No RPM Drop at
Lockup
P0801 Reverse Gear Lockout Circuit Open
or Short P0830 Clutch Depressed Switch Circuit Problem detected in clutch switch circuit. P0833 Clutch Released Switch Circuit Problem detected in clutch switch circuit.
P1110 Decrease Engine Performance Due
To High Intake Air Temperature
P1180 Decreased Engine Performance Due
To High Injection Pump Fuel Temp
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
An open or shorted condition detected in the torque
converter part throttle unlock solenoid control circuit (3 or
4-speed auto. trans. only).
An open or shorted condition detected in the Governor
Pressure Solenoid circuit or Trans Relay Circuit in JTEC
RE transmissions.
An open or shorted condition detected in the governor
pressure solenoid or relay circuits (4-speed auto. trans.
only).
Overdrive override switch input is in a prolonged
depressed state.
Overdrive Off switch input too low for more than 5
minutes (4-speed auto. trans. only).
An open or shorted condition detected in the overdrive
solenoid control circuit or Trans Relay Circuit in JTEC RE
transmissions. Was MIL code 45.
An open or shorted condition detected in the transmission
2-4 shift solenoid circuit (4-speed auto. trans. only).
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.
Intake manifold air temperature is above the engine
protection limit. Engine power will be derated.
Fuel temperature is above the engine protection limit.
Engine power will be derated.
A slow switching oxygen sensor has been detected in
bank 1/1 during catalyst monitor test. (Also see SCI DTC
$66) (was P0133)
A slow switching oxygen sensor has been detected in
bank 2/1 during catalyst monitor test. (Also see SCI DTC
$7A) (was P0153)
A slow switching oxygen sensor has been detected in
bank 1/2 during catalyst monitor test. (Also see SCI DTC
$68) (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).
Page 11
XJ EMISSION CONTROL SYSTEMS 25 - 11
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P1282 Fuel Pump Relay Control Circuit An open or shorted condition detected in the fuel pump
relay control circuit.
P1283 Idle Select Signal Invalid ECM or fuel injection pump module internal fault condition
detected.
P1284 (M) Fuel Injection Pump Battery Voltage
Out-Of-Range
P1285 (M) Fuel Injection Pump Controller
Always On
P1286 Accelerator Position Sensor (APPS)
Supply Voltage Too High
P1287 Fuel Injection Pump Controller
Supply Voltage Low
P1288 Intake Manifold Short Runner
Solenoid Circuit
P1289 Manifold Tune Valve Solenoid Circuit An open or shorted condition detected in the manifold
P1290 CNG Fuel System Pressure Too
High
P1291 No Temp Rise Seen From Intake
Heaters
P1291 (M) No Temperature Rise Seen From
Intake Air 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 (M) No 5 Volts to TP Sensor Loss of a 5 volt feed to the Throttle Position Sensor has
P1295 (M) Accelerator Position Sensor (APPS)
Supply Voltage Too Low
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 Vacuum Leak Found (IAC Fully
Seated)
P1388 Auto Shutdown Relay Control Circuit An open or shorted condition detected in the ASD or CNG
P1388 Auto Shutdown Relay Control Circuit An open or shorted condition detected in the auto
Fuel injection pump module internal fault condition
detected. Engine power will be derated.
Fuel injection pump module relay circuit failure detected.
Engine power will be derated.
High voltage detected at APPS.
ECM or fuel injection pump module internal fault condition
detected. Engine power will be derated.
An open or shorted condition detected in the short runner
tuning valve circuit.
tuning valve solenoid control circuit.
Compressed natural gas system pressure above normal
operating range.
Energizing Heated Air Intake does not change intake air
temperature sensor an acceptable amount.
Problem detected in intake manifold air heating system.
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.
APPS supply voltage input below the minimum
acceptable voltage.
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.
shutdown relay circuit.
Page 12
25 - 12 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P1389 No ASD Relay Output Voltage At
PCM
P1389 (M) No ASD Relay Output Voltage at
PCM
P1390 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 5V to EGR Sens Loss of 5v feed to the EGR position sensor.
P01475 Aux 5 Volt Supply Voltage High Sensor supply voltage for ECM sensors is too high.
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 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
P1481 EATX RPM Pulse Perf EATX RPM pulse generator signal for misfire detection
P1482 Catalyst Temperature Sensor Circuit
Shorted Low
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 Evap Leak Monitor Pinched Hose
Found
P1487 Hi Speed Rad Fan CTRL Relay
Circuit
P1488 Auxiliary 5 Volt Supply Output Too
Low P1488 5 Volt Supply Voltage Low Sensor supply voltage for ECM sensors is too low. P1489 High Speed Fan CTRL Relay Circuit An open or shorted condition detected in the control
P1490 Low Speed Fan CTRL Relay Circuit An open or shorted condition detected in control circuit of
No Z1 or Z2 voltage sensed when the auto shutdown
relay is energized.
An open condition detected In the ASD relay output
circuit.
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.
does not correlate with expected value.
Catalyst temperature sensor circuit shorted low.
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.
Page 13
XJ EMISSION CONTROL SYSTEMS 25 - 13
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P1491 Rad Fan Control Relay Circuit An open or shorted condition detected in the radiator fan
control relay control circuit. This includes PWM solid state
relays.
P1492 Ambient/Batt Temp Sen Volts Too
High
P1492 (M) Ambient/Batt Temp Sensor Volts Too
High
P1493 (M) Ambient/Batt Temp Sen Volts Too
Low
P1493 (M) Ambient/Batt Temp Sen Volts Too
Low
P1494 (M) Leak Detection Pump Sw or
Mechanical Fault
P1495 Leak Detection Pump Solenoid
Circuit
P1496 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
P1594 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
P1595 Speed Control Solenoid Circuits An open or shorted condition detected in the speed
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
P1597 Speed Control Switch Always Low Speed control switch input below the minimum acceptable
P1598 A/C Pressure Sensor Volts Too High A/C pressure sensor input above maximum acceptable
P1598 A/C Sensor Input Hi Problem detected in air conditioning electrical circuit. P1599 A/C Pressure Sensor Volts Too Low A/C pressure sensor input below minimum acceptable
P1599 A/C Sensor Input Lo Problem detected in air conditioning electrical circuit. P1680 Clutch Released Switch Circuit Problem detected in clutch switch electrical circuit. P1681 No I/P Cluster CCD/J1850
Messages Received
External temperature sensor input above acceptable
voltage.
Battery temperature sensor input voltage above an
acceptable range.
External temperature sensor input below acceptable
voltage.
Battery temperature sensor input voltage below an
acceptable range.
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. ( less than 4v for 4 sec )
An open or shorted condition detected in the control
circuit of the #3 high speed radiator fan control relay.
during engine operation.
during engine operation.
speed control vacuum or vent solenoid control circuits.
control vacuum or vent solenoid circuits.
voltage.
voltage.
voltage.
voltage.
voltage.
No CCD/J1850 messages received from the cluster
control module.
Page 14
25 - 14 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
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. P1682 Charging System Voltage Too Low Charging system output voltage low. P1683 SPD CTRL PWR Relay; or S/C 12v
Driver CKT
P1683 Spd ctrl pwr rly, or s/c 12v driver
circuit
P1684 Batt Loss in 50 Star 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
P1688 (M) Internal Fuel Injection Pump
Controller Failure
P1689 (M) No Communication Between ECM
and Injection Pump Module
P1690 (M) Fuel Injection Pump CKP Sensor
Does Not Agree With ECM CKP
Sensor
P1691 Fuel Injection Pump Controller
Calibration Error
P1692 DTC Set In ECM A “Companion DTC” was set in both the ECM and PCM.
P1693 (M) DTC Detected in Companion Module A fault has been generated in the companion engine
P1693 (M) DTC Detected in PCM/ECM or DTC
Detected in ECM
P1694 Fault In Companion Module No CCD/J1850 messages received from the powertrain
P1694 (M) No CCD Messages received from
ECM
P1695 No CCD/J1850 Message From Body
Control Module
P1696 PCM Failure EEPROM Write Denied Unsuccessful attempt to write to an EEPROM location by
P1697 PCM Failure SRI Mile Not Stored Unsuccessful attempt to update Service Reminder
P1698 No CCD/J1850 Message From TCM No CCD/J1850 messages received from the electronic
An open or shorted condition detected in the speed
control servo power control circuit.
An open or shorted condition detected in the speed
control servo power control circuit.
starts
SKIM.
Immobilizer Module (SKIM).
Instrument Cluster (MIC) module.
Internal problem within the fuel injection pump. Low
power, engine derated, or engine stops.
Data link circuit failure between ECM and fuel injection
pump. Low power, engine derated, or engine stops.
Problem in fuel sync signal. Possible injection pump
timing problem. Low power, engine derated, or engine
stops.
Internal fuel injection pump failure. Low power, engine
derated, or engine stops.
control module.
A “Companion DTC” was set in both the ECM and PCM.
control module-Aisin transmission
Bus communication failure to PCM.
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.
Page 15
XJ EMISSION CONTROL SYSTEMS 25 - 15
DESCRIPTION AND OPERATION (Continued)
(M) Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was
recorded (depending if required by CARB and/or EPA). MIL is displayed as an engine icon on
instrument panel.
P1698 No CCD Messages received from
PCM
P1719 Skip Shift Solenoid Circuit An open or shorted condition detected in the transmission
P1740 TCC or OD Sol Perf A rationality error has been detected in either the TCC
P1740 (M) TCC OR O/D Solenoid Performance Problem detected in transmission convertor clutch and/or
P1756 (M) GOV Press Not Equal to Target @
15-20 PSI
P1756 (M) Governor Pressure Not Equal to
Target @ 15-20 PSI
P1757 GOV Press Not Equal to Target @
15-20 PSI
P1757 (M) Governor Pressure Above 3 PSI In
Gear With 0 MPH
P1762 (M) Gov Press Sen Offset Volts Too Lo
or High
P1762 (M) Governor Press Sen Offset Volts Too
Low or High
P1763 Governor Pressure Sensor Volts Too
Hi
P1763 (M) Governor Pressure Sensor Volts Too
HI
P1764 (M) Governor Pressure Sensor Volts Too
Low
P1764 (M) Governor Pressure Sensor Volts Too
Low
P1765 (M) Trans 12 Volt Supply Relay CTRL
Circuit
P1765 (M) 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. P1899 (M) P/N Switch Stuck in Park or in Gear Incorrect input state detected for the Park/Neutral switch
Bus communication failure to PCM. A “Companion DTC”
was set in both the ECM and PCM.
2-3 gear lock-out solenoid control circuit.
solenoid or overdrive solenoid systems.
overdrive circuits (diesel engine with 4-speed auto. trans.
only).
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)
Governor sensor input not between 10 and 25 psi when
requested (4-speed auto. trans. only).
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)
Governor pressure greater than 3 psi when requested to
be 0 psi (4-speed auto. trans. only).
The Governor Pressure Sensor input is greater than a
calibration limit or is less than a calibration limit for 3
consecutive park/neutral calibrations.
Sensor input greater or less than calibration for 3
consecutive Neutral/Park occurrences (4-speed auto.
trans. only).
The Governor Pressure Sensor input is above an
acceptable voltage level.
Voltage greater than 4.89 volts (4-speed auto. trans.
only).
The Governor Pressure Sensor input is below an
acceptable voltage level.
Voltage less than.10 volts (4-speed auto. trans. only).
An open or shorted condition is detected in the
Transmission Relay control circuit. This relay supplies
power to the TCC
Current state of solenoid output port is different than
expected (4-speed auto. trans. only).
(3 or 4-speed auto. trans. only).
Page 16
25 - 16 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)

TASK MANAGER

DESCRIPTION
The PCM is responsible for efficiently coordinating the operation of all the emissions-related compo­nents. The PCM is also responsible for determining if the diagnostic systems are operating properly. The software designed to carry out these responsibilities is call the ’Task Manager’.
OPERATION
The Task Manager determines which tests happen when and which functions occur when. Many of the diagnostic steps required by OBD II must be per­formed under specific operating conditions. The Task Manager software organizes and prioritizes the diag­nostic procedures. The job of the Task Manager is to determine if conditions are appropriate for tests to be run, monitor the parameters for a trip for each test, and record the results of the test. Following are the responsibilities of the Task Manager software:
• Test Sequence
• MIL Illumination
• Diagnostic Trouble Codes (DTCs)
• Trip Indicator
• Freeze Frame Data Storage
• Similar Conditions Window
Test Sequence
In many instances, emissions systems must fail diagnostic tests more than once before the PCM illu­minates the MIL. These tests are know as ’two trip monitors.’ Other tests that turn the MIL lamp on after a single failure are known as ’one trip moni­tors.’ A trip is defined as ’start the vehicle and oper­ate it to meet the criteria necessary to run the given monitor.’
Many of the diagnostic tests must be performed under certain operating conditions. However, there are times when tests cannot be run because another test is in progress (conflict), another test has failed (pending) or the Task Manager has set a fault that may cause a failure of the test (suspend).
• Pending Under some situations the Task Manager will not run a monitor if the MIL is illuminated and a fault is stored from another monitor. In these situations, the Task Manager postpones monitors pending resolu­tion of the original fault. The Task Manager does not run the test until the problem is remedied. For example, when the MIL is illuminated for an Oxygen Sensor fault, the Task Manager does not run the Catalyst Monitor until the Oxygen Sensor fault is remedied. Since the Catalyst Monitor is based on sig­nals from the Oxygen Sensor, running the test would produce inaccurate results.
• Conflict There are situations when the Task Manager does not run a test if another monitor is in progress. In these situations, the effects of another monitor run­ning could result in an erroneous failure. If this con- flict is present, the monitor is not run until the conflicting condition passes. Most likely the monitor will run later after the conflicting monitor has passed. For example, if the Fuel System Monitor is in progress, the Task Manager does not run the EGR Monitor. Since both tests monitor changes in air/fuel ratio and adaptive fuel compensation, the monitors will conflict with each other.
• Suspend Occasionally the Task Manager may not allow a two trip fault to mature. The Task Manager will sus- pend the maturing of a fault if a condition exists that may induce an erroneous failure. This prevents illuminating the MIL for the wrong fault and allows more precis diagnosis. For example, if the PCM is storing a one trip fault for the Oxygen Sensor and the EGR monitor, the Task Manager may still run the EGR Monitor but will suspend the results until the Oxygen Sensor Monitor either passes or fails. At that point the Task Manager can determine if the EGR system is actu­ally failing or if an Oxygen Sensor is failing.
MIL Illumination
The PCM Task Manager carries out the illumina­tion of the MIL. The Task Manager triggers MIL illu­mination upon test failure, depending on monitor failure criteria.
The Task Manager Screen shows both a Requested MIL state and an Actual MIL state. When the MIL is illuminated upon completion of a test for a third trip, the Requested MIL state changes to OFF. However, the MIL remains illuminated until the next key cycle. (On some vehicles, the MIL will actually turn OFF during the third key cycle) During the key cycle for the third good trip, the Requested MIL state is OFF, while the Actual MILL state is ON. After the next key cycle, the MIL is not illuminated and both MIL states read OFF.
Diagnostic Trouble Codes (DTCs)
With OBD II, different DTC faults have different priorities according to regulations. As a result, the priorities determine MIL illumination and DTC era­sure. DTCs are entered according to individual prior­ity. DTCs with a higher priority overwrite lower priority DTCs.
Priorities
• Priority 0 —Non-emissions related trouble codes
Page 17
XJ EMISSION CONTROL SYSTEMS 25 - 17
DESCRIPTION AND OPERATION (Continued)
• Priority 1 — One trip failure of a two trip fault
for non-fuel system and non-misfire.
• Priority 2 — One trip failure of a two trip fault
for fuel system (rich/lean) or misfire.
• Priority3—Twotrip failure for a non-fuel sys­tem and non-misfire or matured one trip comprehen­sive component fault.
• Priority4—Twotrip failure or matured fault for fuel system (rich/lean) and misfire or one trip cat­alyst damaging misfire.
Non-emissions related failures have no priority. One trip failures of two trip faults have low priority. Two trip failures or matured faults have higher pri­ority. One and two trip failures of fuel system and misfire monitor take precedence over non-fuel system and non-misfire failures.
DTC Self Erasure
With one trip components or systems, the MIL is illuminated upon test failure and DTCs are stored.
Two trip monitors are components requiring failure in two consecutive trips for MIL illumination. Upon failure of the first test, the Task Manager enters a maturing code. If the component fails the test for a second time the code matures and a DTC is set.
After three good trips the MIL is extinguished and the Task Manager automatically switches the trip counter to a warm-up cycle counter. DTCs are auto­matically erased following 40 warm-up cycles if the component does not fail again.
For misfire and fuel system monitors, the compo­nent must pass the test under a Similar Conditions Window in order to record a good trip. A Similar Con­ditions Window is when engine RPM is within 6375 RPM and load is within 610% of when the fault occurred.
NOTE: It is important to understand that a compo­nent does not have to fail under a similar window of operation to mature. It must pass the test under a Similar Conditions Window when it failed to record a Good Trip for DTC erasure for misfire and fuel system monitors.
DTCs can be erased anytime with a DRB III. Eras­ing the DTC with the DRB III erases all OBD II information. The DRB III automatically displays a warning that erasing the DTC will also erase all OBD II monitor data. This includes all counter infor­mation for warm-up cycles, trips and Freeze Frame.
Trip Indicator
The Trip is essential for running monitors and extinguishing the MIL. In OBD II terms, a trip is a set of vehicle operating conditions that must be met for a specific monitor to run. All trips begin with a key cycle.
Good Trip
The Good Trip counters are as follows:
• Specific Good Trip
• Fuel System Good Trip
• Misfire Good Trip
• Alternate Good Trip (appears as a Global Good
Trip on DRB III)
• Comprehensive Components
• Major Monitor
• Warm-Up Cycles
Specific Good Trip
The term Good Trip has different meanings
depending on the circumstances:
• If the MIL is OFF, a trip is defined as when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed in the same drive cycle.
• If the MIL is ON and a DTC was set by the Fuel Monitor or Misfire Monitor (both continuous moni­tors), the vehicle must be operated in the Similar Condition Window for a specified amount of time.
• If the MIL is ON and a DTC was set by a Task Manager commanded once-per-trip monitor (such as the Oxygen Sensor Monitor, Catalyst Monitor, Purge Flow Monitor, Leak Detection Pump Monitor, EGR Monitor or Oxygen Sensor Heater Monitor), a good trip is when the monitor is passed on the next start­up.
• If the MIL is ON and any other emissions DTC was set (not an OBD II monitor), a good trip occurs when the Oxygen Sensor Monitor and Catalyst Mon­itor have been completed, or two minutes of engine run time if the Oxygen Sensor Monitor and Catalyst Monitor have been stopped from running.
Fuel System Good Trip
To count a good trip (three required) and turn off
the MIL, the following conditions must occur:
• Engine in closed loop
• Operating in Similar Conditions Window
• Short Term multiplied by Long Term less than
threshold
• Less than threshold for a predetermined time
If all of the previous criteria are met, the PCM will count a good trip (three required) and turn off the MIL.
Misfire Good Trip
If the following conditions are met the PCM will count one good trip (three required) in order to turn off the MIL:
• Operating in Similar Condition Window
• 1000 engine revolutions with no misfire
Warm-Up Cycles
Once the MIL has been extinguished by the Good Trip Counter, the PCM automatically switches to a Warm-Up Cycle Counter that can be viewed on the DRB III. Warm-Up Cycles are used to erase DTCs and Freeze Frames. Forty Warm-Up cycles must
Page 18
25 - 18 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
occur in order for the PCM to self-erase a DTC and Freeze Frame. A Warm-Up Cycle is defined as fol­lows:
• Engine coolant temperature must start below
and rise above 160° F
• Engine coolant temperature must rise by 40° F
• No further faults occur
Freeze Frame Data Storage
Once a failure occurs, the Task Manager records several engine operating conditions and stores it in a Freeze Frame. The Freeze Frame is considered one frame of information taken by an on-board data recorder. When a fault occurs, the PCM stores the input data from various sensors so that technicians can determine under what vehicle operating condi­tions the failure occurred.
The data stored in Freeze Frame is usually recorded when a system fails the first time for two trip faults. Freeze Frame data will only be overwrit­ten by a different fault with a higher priority.
CAUTION: Erasing DTCs, either with the DRB III or by disconnecting the battery, also clears all Freeze Frame data.
Similar Conditions Window
The Similar Conditions Window displays informa­tion about engine operation during a monitor. Abso­lute MAP (engine load) and Engine RPM are stored in this window when a failure occurs. There are two different Similar conditions Windows: Fuel System and Misfire.
FUEL SYSTEM
• Fuel System Similar Conditions Window — An indicator that ’Absolute MAP When Fuel Sys Fail’ and ’RPM When Fuel Sys Failed’ are all in the same range when the failure occurred. Indicated by switch­ing from ’NO’ to ’YES’.
• Absolute MAP When Fuel Sys Fail — The stored MAP reading at the time of failure. Informs the user at what engine load the failure occurred.
• Absolute MAP — A live reading of engine load to aid the user in accessing the Similar Conditions Window.
• RPM When Fuel Sys Fail — The stored RPM reading at the time of failure. Informs the user at what engine RPM the failure occurred.
• Engine RPM — A live reading of engine RPM to aid the user in accessing the Similar Conditions Window.
• Adaptive Memory Factor — The PCM uti- lizes both Short Term Compensation and Long Term Adaptive to calculate the Adaptive Memory Factor for total fuel correction.
• Upstream O2S Volts — A live reading of the Oxygen Sensor to indicate its performance. For example, stuck lean, stuck rich, etc.
• SCW Time in Window (Similar Conditions Window Time in Window) — A timer used by the
PCM that indicates that, after all Similar Conditions have been met, if there has been enough good engine running time in the SCW without failure detected. This timer is used to increment a Good Trip.
• Fuel System Good Trip Counter —ATrip Counter used to turn OFF the MIL for Fuel System DTCs. To increment a Fuel System Good Trip, the engine must be in the Similar Conditions Window, Adaptive Memory Factor must be less than cali­brated threshold and the Adaptive Memory Factor must stay below that threshold for a calibrated amount of time.
• Test Done This Trip — Indicates that the monitor has already been run and completed during the current trip.
MISFIRE
• Same Misfire Warm-Up State — Indicates if the misfire occurred when the engine was warmed up (above 160° F).
• In Similar Misfire Window — An indicator that ’Absolute MAP When Misfire Occurred’ and ’RPM When Misfire Occurred’ are all in the same range when the failure occurred. Indicated by switch­ing from ’NO’ to ’YES’.
• Absolute MAP When Misfire Occurred — The stored MAP reading at the time of failure. Informs the user at what engine load the failure occurred.
• Absolute MAP — A live reading of engine load to aid the user in accessing the Similar Conditions Window.
• RPM When Misfire Occurred — The stored RPM reading at the time of failure. Informs the user at what engine RPM the failure occurred.
• Engine RPM — A live reading of engine RPM to aid the user in accessing the Similar Conditions Window.
• Adaptive Memory Factor — The PCM uti- lizes both Short Term Compensation and Long Term Adaptive to calculate the Adaptive Memory Factor for total fuel correction.
• 200 Rev Counter — Counts 0–100 720 degree cycles.
• SCW Cat 200 Rev Counter — Counts when in similar conditions.
• SCW FTP 1000 Rev Counter — Counts 0–4 when in similar conditions.
• Misfire Good Trip Counter — Counts up to three to turn OFF the MIL.
• Misfire Data — Data collected during test.
Page 19
XJ EMISSION CONTROL SYSTEMS 25 - 19
DESCRIPTION AND OPERATION (Continued)
• Test Done This Trip — Indicates YES when
the test is done.

MONITORED SYSTEMS

OPERATION
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 Lamp (MIL) will be illuminated. These monitors generate Diagnostic Trouble Codes that can be displayed with the MIL or a scan tool.
The following is a list of the system monitors:
• Misfire Monitor
• Fuel System Monitor
• Oxygen Sensor Monitor
• Oxygen Sensor Heater Monitor
• Catalyst Monitor
• Leak Detection Pump Monitor (if equipped)
All these system monitors require two consecutive trips with the malfunction present to set a fault.
Refer to the appropriate Powertrain Diagnos­tics Procedures manual for diagnostic proce­dures.
The following is an operation and description of each system monitor :
OXYGEN SENSOR (O2S) MONITOR
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. 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 nitrogen oxide (NOx) from the exhaust.
The O2S is also the main sensing element for the Catalyst and Fuel Monitors.
The O2S can fail in any or all of the following manners:
• slow response rate
• reduced output voltage
• dynamic shift
• shorted or open circuits
Response rate is the time required for the sensor to switch from lean to rich once it is exposed to a richer than optimum A/F mixture or vice versa. As the sen­sor starts malfunctioning, it could take longer to detect the changes in the oxygen content of the exhaust gas.
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.
OXYGEN SENSOR HEATER MONITOR
If there is an oxygen sensor (O2S) shorted to volt­age DTC, as well as a O2S heater DTC, the O2S fault MUST be repaired first. Before checking the O2S fault, verify that the heater circuit is operating correctly.
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. 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 nitrogen oxide (NOx) from the exhaust.
The voltage readings taken from the O2S sensor are very temperature sensitive. The readings are not accurate below 300°C. Heating of the O2S sensor 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 sensor must be tested to ensure that it is heating the sensor properly.
The O2S sensor circuit is monitored for a drop in voltage. The sensor output is used to test the heater by isolating the effect of the heater element on the O2S sensor output voltage from the other effects.
LEAK DETECTION PUMP MONITOR (IF EQUIPPED)
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 func-
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25 - 20 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
tions 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.
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.
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 sensor 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 fuel-air ratio with the O2S sensor (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.
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’s sensor strategy is based on the fact that
Page 21
XJ EMISSION CONTROL SYSTEMS 25 - 21
DESCRIPTION AND OPERATION (Continued)
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 will be illu­minated.

TRIP DEFINITION

OPERATION
The term “Trip” has different meanings depending on what the circumstances are. If the MIL (Malfunc­tion Indicator Lamp) is OFF, a Trip is defined as when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed in the same drive cycle.
When any Emission DTC is set, the MIL on the dash is turned ON. When the MIL is ON, it takes 3 good trips to turn the MIL OFF. In this case, it depends on what type of DTC is set to know what a “Trip” is.
For the Fuel Monitor or Mis-Fire Monitor (contin­uous monitor), the vehicle must be operated in the
“Similar Condition Window” for a specified amount of time to be considered a Good Trip.
If a Non-Contiuous OBDII Monitor, such as:
• Oxygen Sensor
• Catalyst Monitor
• Purge Flow Monitor
• Leak Detection Pump Monitor (if equipped)
• EGR Monitor (if equipped)
• Oxygen Sensor Heater Monitor
fails twice in a row and turns ON the MIL, re-run­ning that monitor which previously failed, on the next start-up and passing the monitor is considered to be a Good Trip.
If any other Emission DTC is set (not an OBDII Monitor), a Good Trip is considered to be when the Oxygen Sensor Monitor and Catalyst Monitor have been completed; or 2 Minutes of engine run time if the Oxygen Sensor Monitor or Catalyst Monitor have been stopped from running.
It can take up to 2 Failures in a row to turn on the MIL. After the MIL is ON, it takes 3 Good Trips to turn the MIL OFF. After the MIL is OFF, the PCM will self-erase the DTC after 40 Warm-up cycles. A Warm-up cycle is counted when the ECT (Engine Coolant Temperature Sensor) has crossed 160°F and has risen by at least 40°F since the engine has been started.

COMPONENT MONITORS

OPERATION
There are several components that will affect vehi­cle emissions if they malfunction. If one of these com­ponents malfunctions the Malfunction Indicator Lamp (MIL) 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 if the TPS indicates a small throttle opening.
All open/short circuit checks or any component that has an associated limp in will set a fault after 1 trip with the malfunction present. Components without an associated limp in will take two trips to illumi­nate the MIL.
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25 - 22 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
Refer to the Diagnostic Trouble Codes Description Charts in this section and the appropriate Power­train Diagnostic Procedure Manual for diagnostic procedures.

NON-MONITORED CIRCUITS

The PCM does not monitor the following circuits, systems and conditions that could have malfunctions causing driveability problems. The PCM might not store diagnostic trouble codes for these conditions. 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
OPERATION
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.
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.
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.
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, although it may set a fuel system fault.
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.

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.

LOAD VALUE

OPERATION
ENGINE IDLE/NEUTRAL 2500 RPM/
NEUTRAL
All Engines 2% to 8% of
Maximum Load
9% to 17% of
Maximum Load
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XJ EMISSION CONTROL SYSTEMS 25 - 23

EVAPORATIVE EMISSION CONTROLS

TABLE OF CONTENTS
page page

DESCRIPTION AND OPERATION

EVAPORATION CONTROL SYSTEM ..........23
ROLLOVER VALVE .......................23
EVAP CANISTER .........................24
DUTY CYCLE EVAP CANISTER PURGE
SOLENOID ............................24
LEAK DETECTION PUMP (LDP)..............24
CRANKCASE VENTILATION SYSTEM .........25
VEHICLE EMISSION CONTROL
INFORMATION (VECI) LABEL ..............26
DIAGNOSIS AND TESTING
VACUUM SCHEMATICS....................26
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 a charcoal 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 duty cycle purge system. The PCM controls vapor flow by operating the duty cycle EVAP purge solenoid. Refer to Duty Cycle EVAP Canister Purge Solenoid.
When equipped with certain emissions packages, a Leak Detection Pump (LDP) will be used as part of the evaporative system for OBD II requirements. Also refer to Leak Detection Pump.
NOTE: The evaporative system uses specially man­ufactured lines/hoses. If replacement becomes nec­essary, only use fuel resistant hose.

ROLLOVER VALVE

LEAK DETECTION PUMP (LDP)..............27
CRANKCASE VENTILATION SYSTEM .........27
REMOVAL AND INSTALLATION
EVAP CANISTER .........................27
DUTY CYCLE EVAP CANISTER PURGE
SOLENOID ............................27
ROLLOVER VALVE(S) .....................27
LEAK DETECTION PUMP (LDP)..............28
SPECIFICATIONS
TORQUE CHART .........................28
Fig. 1 Rollover Valve Location
1 – ROLLOVER VALVE 2 – RETAINER CLAMP 3 – LOCKNUT 4 – FUEL PUMP MODULE 5 – FUEL FILTER/FUEL PRESSURE REGULATOR 6 – ALIGNMENT ARROW 7 – PIGTAIL HARNESS 8 – FUEL SUPPLY TUBE 9 – EVAP CANISTER VENT LINE
DESCRIPTION
The fuel tank is equipped with a rollover valve.
The valve is located on the top of the fuel tank (Fig.
1).
OPERATION
The rollover valve will prevent fuel flow through the fuel tank vent (EVAP) hoses in the event of an accidental vehicle rollover. The EVAP canister draws fuel vapors from the fuel tank through this valve.
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25 - 24 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
The valve cannot be serviced separately. If replace-
ment is necessary, the fuel tank must be replaced.

EVAP CANISTER

DESCRIPTION
A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is located under the left side of vehicle near the front of the rear axle (Fig. 2).
Fig. 2 EVAP Canister Location
1 – CANISTER MOUNTING BRACKET 2 – BRACKET NUTS (3) 3 – EVAP CANISTER 4 – CANISTER MOUNTING NUTS (2) 5 – L. R. SHOCK ABSORBER 6 – EVAP LINES/HOSES 7 – DOWEL PINS AND BUSHINGS (2)
OPERATION
The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.
Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.

DUTY CYCLE EVAP CANISTER PURGE SOLENOID

OPERATION
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP can­ister to the intake manifold. The Powertrain Control Module (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 PCM de-energizes the solenoid during open loop oper­ation.
The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second, depending upon operating condi­tions. The PCM varies the vapor flow rate by chang­ing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operat­ing condition.

LEAK DETECTION PUMP (LDP)

OPERATION
The Leak Detection Pump (LDP) is used only with certain emission packages.
The LDP 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.
Immediately after a cold start, engine temperature 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.
Page 25
XJ EMISSION CONTROL SYSTEMS 25 - 25
DESCRIPTION AND OPERATION (Continued)
Fig. 3 Evaporative System Monitor Schematic—Typical
1 – DUTY CYCLE PURGE SOLENOID (DCPS) DRIVER 2 – POWERTRAIN CONTROL MODULE (PCM) 3 – 3-PORT SOLENOID DRIVER 4 – REMOTE FILTER 5 – COMBINED CANISTER VENT VALVE & LEAK DETECTION
PUMP
6 – CANISTER
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.
A typical system schematic is shown in (Fig. 3).

CRANKCASE VENTILATION SYSTEM

DESCRIPTION
All 2.5L 4–cylinder and 4.0L 6–cylinder engines are equipped with a Closed Crankcase Ventilation (CCV) system (Fig. 4) or (Fig. 5).
7 – TANK ROLLOVER VALVE & VAPOR FLOW CONTROL
ORIFICE 8 – INTAKE MANIFOLD 9 – THROTTLE BODY 10 – DCPS 11 – SWITCH SIGNAL INPUT TO THE PCM 12 – ENGINE VACUUM LINE
OPERATION
The CCV system performs the same function as a conventional PCV system, but does not use a vacuum controlled valve.
On 4.0L 6 cylinder engines, a molded vacuum tube connects manifold vacuum to top of cylinder head (valve) cover at dash panel end. The vacuum fitting contains a fixed orifice of a calibrated size. It meters the amount of crankcase vapors drawn out of the engine.
On 2.5L 4 cylinder engines, a fitting on drivers side of cylinder head (valve) cover contains the metered orifice. It is connected to manifold vacuum.
A fresh air supply hose from the air cleaner is con­nected to front of cylinder head cover on 4.0L engines. It is connected to rear of cover on 2.5L engines.
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25 - 26 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
fixed orifice and into the intake manifold. The vapors are then consumed during combustion.

VEHICLE EMISSION CONTROL INFORMATION (VECI) LABEL

DESCRIPTION
All vehicles are equipped with a combined VECI label. This label is located in the engine compart­ment (Fig. 6).
Fig. 4 CCV System—2.5L Engine—Typical
1 – AIR INLET FITTING 2 – AIR FILTER COVER 3 – FIXED ORIFICE FITTING
Fig. 6 VECI Label Location—Typical
1 – VECI LABEL
OPERATION
The VECI label contains the following:
• Engine family and displacement
• Evaporative family
• Emission control system schematic
• Certification application
• Engine timing specifications (if adjustable)
• Idle speeds (if adjustable)
• Spark plug and gap
The label also contains an engine vacuum sche­matic. There are unique labels for vehicles built for sale in the state of California and the country of Canada. Canadian labels are written in both the English and French languages. These labels are per­manently attached and cannot be removed without defacing information and destroying label.
Fig. 5 CCV System—4.0L Engine—Typical
1 – AIR INLET FITTING 2 – FIXED ORIFICE FITTING 3 – AIR FILTER COVER
When the engine is operating, fresh air enters the engine and mixes with crankcase vapors. Manifold vacuum draws the vapor/air mixture through the

DIAGNOSIS AND TESTING

VACUUM SCHEMATICS

A vacuum schematic for emission related items can be found on the Vehicle Emission Control Informa­tion (VECI) label. For label location, refer to Vehicle Emission Control Information (VECI) Label.
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XJ EMISSION CONTROL SYSTEMS 25 - 27
DIAGNOSIS AND TESTING (Continued)

LEAK DETECTION PUMP (LDP)

Refer to the appropriate Powertrain Diagnostic Procedures service manual for LDP testing proce­dures.

CRANKCASE VENTILATION SYSTEM

TESTING/CLEANING
The Crankcase Ventilation (CCV) system performs the same function as a conventional PCV system, but does not use a vacuum controlled valve. A vacuum fitting containing a fixed orifice of a calibrated size is used. It meters the amount of crankcase vapors drawn out of the engine.
(1) Check each CCV system tube (line) for leaks, cracks, kinks or bends. Replace as necessary
(2) Disconnect each CCV tube..
(3) Blow compressed air through each tube and check for blockage or restrictions. If cleaning is nec­essary, spray a soapy-type all-purpose cleaner into each component and blow out. After restriction is cleared, rinse out component with clear water. Blow water from component and install to vehicle. To pre-
vent damage to plastic components, never spray carburetor-type cleaner into any of the plastic tubes or the fixed orifice fitting. Never attempt to clean the fixed orifice fitting with a metal object as calibration could be affected. If fixed fitting cannot be cleared, replace it.
1 – CANISTER MOUNTING BRACKET 2 – BRACKET NUTS (3) 3 – EVAP CANISTER 4 – CANISTER MOUNTING NUTS (2) 5 – L. R. SHOCK ABSORBER 6 – EVAP LINES/HOSES 7 – DOWEL PINS AND BUSHINGS (2)

DUTY CYCLE EVAP CANISTER PURGE SOLENOID

Fig. 7 EVAP Canister Location

REMOVAL AND INSTALLATION

EVAP CANISTER

The EVAP canister is located under left side of vehicle near front of rear axle (Fig. 7).
REMOVAL
(1) Disconnect vacuum hoses/lines at EVAP canis­ter. Note location of lines before removal.
(2) Remove EVAP canister and mounting bracket assembly from body (3 nuts).
(3) Remove canister from mounting bracket (2 nuts).
INSTALLATION
(1) Position canister into canister mounting bracket. Align 2 canister dowel pins into rubber bushings.
(2) Install 2 canister nuts and tighten to 5 N·m (45 in. lbs.) torque.
(3) Position canister and bracket assembly to body.
(4) Install 3 nuts and tighten to 43 N·m (32 ft. lbs.) torque.
(5) Connect vacuum hoses/lines at EVAP canister.
REMOVAL
The solenoid attaches to a bracket located in right­rear side of engine compartment (Fig. 8) or (Fig. 9). The top of the solenoid has the word UP or TOP on it. The solenoid will not operate properly unless it is installed correctly.
(1) Disconnect electrical wiring connector at sole­noid.
(2) Disconnect vacuum harness at solenoid.
(3) Remove solenoid and its support bracket.
INSTALLATION
(1) Install EVAP canister purge solenoid and its mounting bracket to cowl panel.
(2) Tighten bolt to 5 N·m (45 in. lbs.) torque.
(3) Connect vacuum harness and wiring connector.

ROLLOVER VALVE(S)

The rollover valves(s) are/is molded into the fuel tank and are not serviced separately. If replacement is necessary, the fuel tank must be replaced. Refer to Fuel Tank Removal/Installation.
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25 - 28 EMISSION CONTROL SYSTEMS XJ
REMOVAL AND INSTALLATION (Continued)

LEAK DETECTION PUMP (LDP)

The LDP is located in the right-rear side of engine compartment (Fig. 9). The LDP filter is located above the LDP (Fig. 9). The LDP and LDP filter are replaced (serviced) as one unit.
REMOVAL
(1) Carefully remove hose at LDP filter.
(2) Remove LDP filter mounting bolt and remove from vehicle.
(3) Carefully remove vapor/vacuum lines at LDP.
(4) Disconnect electrical connector at LDP.
(5) Remove 2 LDP mounting screws (Fig. 9) and remove from vehicle.
Fig. 8 EVAP Canister Purge Solenoid (Without LDP)
1 – ELECTRICAL CONNECTOR 2 – VACUUM HARNESS 3 – PURGE SOLENOID 4 – MOUNTING BOLT
Fig. 9 EVAP Canister Purge Solenoid (With LDP)
1 – LDP FILTER 2 – EVAP SOLENOID 3 – EVAP SYSTEM TEST PORT 4 – EVAP SOLENOID ELEC. CONNECTOR 5 – LDP ELEC. CONNECTOR 6 – LDP MOUNTING SCREWS (2) 7 – LDP 8 – LDP MOUNTING BRACKET
INSTALLATION
(1) Install LDP to mounting bracket. Tighten screws to 1 N·m (11 in. lbs.) torque.
(2) Install LDP filter to mounting bracket. Tighten bolt to 7 N·m (65 in. lbs.) torque.
(3) Carefully install vapor/vacuum lines to LDP, and install hose to LDP filter. The vapor/vacuum
lines and hoses must be firmly connected. Check the vapor/vacuum lines at the LDP, LDP filter and EVAP canister purge solenoid for damage or leaks. If a leak is present, a Diagnos­tic Trouble Code (DTC) may be set.
(4) Connect electrical connector to LDP.

SPECIFICATIONS

TORQUE CHART

Description Torque
EVAP Canister Mounting Nuts (canister-to-
mounting bracket) ......... 5N·m(45in.lbs.)
EVAP Canister Mounting Bracket Nuts (mounting
bracket-to-body) .......... 43N·m(32in.lbs.)
EVAP Canister Purge Solenoid Bracket-to-Body
Mounting Bolt ............ 5N·m(45in.lbs.)
LDP Mounting Screws ........ 1N·m(11in.lbs.)
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