Dodge Speed Control Service Manual
DR SPEED CONTROL 8P - 1
SPEED CONTROL
TABLE OF CONTENTS
page page
SPEED CONTROL
DESCRIPTION ..........................1
OPERATION ............................2
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - VACUUM
SUPPLY TEST .........................2
DIAGNOSIS AND TESTING - ROAD TEST ....3
SPECIFICATIONS
TORQUE - SPEED CONTROL .............3
CABLE
DESCRIPTION ..........................3
OPERATION ............................3
REMOVAL .............................3
INSTALLATION ..........................6
SERVO
DESCRIPTION ..........................6
SPEED CONTROL
DESCRIPTION
All 3.7L/4.7L/5.9L/8.0LGas Engines and/or Diesel
With Automatic Trans.
The speed control system is operated by the use of
a cable and a vacuum controlled servo. Electronic
control of the speed control system is integrated into
the Powertrain Control Module (PCM). The controls
consist of two steering wheel mounted switches. The
switches are labeled: ON/OFF, RES/ACCEL, SET,
COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
OPERATION ............................7
REMOVAL .............................7
INSTALLATION ..........................7
SWITCH
DESCRIPTION ..........................8
OPERATION ............................8
REMOVAL .............................9
INSTALLATION ..........................9
VACUUM RESERVOIR
DESCRIPTION ..........................9
OPERATION ............................9
DIAGNOSIS AND TESTING - VACUUM
RESERVOIR ..........................9
REMOVAL .............................10
INSTALLATION .........................10
switches are labeled: ON/OFF, RES/ACCEL, SET,
COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
5.9L Diesel With Manual Trans.
The speed control system is fully electronically con-
trolled by the Engine Control Module (ECM). A
cable and a vacuum controlled servo are not
used if the vehicle is equipped with a manual
transmission and a diesel engine. This is a servo-less system. The controls consist of two steering
wheel mounted switches. The switches are labeled:
ON/OFF, RES/ACCEL, SET, COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
5.7L Gas
The speed control system is fully electronically con-
trolled by the Powertrain Control Module (PCM). A
cable and a vacuum controlled servo are not
used. This is a servo-less system. The controls
consist of two steering wheel mounted switches. The
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
8P - 2 SPEED CONTROL DR
SPEED CONTROL (Continued)
OPERATION
When speed control is selected by depressing the
ON switch, the PCM (the ECM with a diesel engine)
allows a set speed to be stored in its RAM for speed
control. To store a set speed, depress the SET switch
while the vehicle is moving at a speed between 35
and 85 mph. In order for the speed control to engage,
the brakes cannot be applied, nor can the gear selector be indicating the transmission is in Park or Neutral.
The speed control can be disengaged manually by:
• Stepping on the brake pedal
• Depressing the OFF switch
• Depressing the CANCEL switch.
• Depressing the clutch pedal (if equipped).
NOTE: Depressing the OFF switch or turning off the
ignition switch will erase the set speed stored in
the PCM (the ECM with a diesel engine).
For added safety, the speed control system is programmed to disengage for any of the following conditions:
• An indication of Park or Neutral
• A rapid increase rpm (indicates that the clutch
has been disengaged)
• Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
• The speed signal increases at a rate of 10 mph
per second (indicates that the coefficient of friction
between the road surface and tires is extremely low)
• The speed signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
Once the speed control has been disengaged,
depressing the RES/ACCEL switch (when speed is
greater than 30 mph) restores the vehicle to the target speed that was stored in the PCM (the ECM with
a diesel engine).
While the speed control is engaged, the driver can
increase the vehicle speed by depressing the RES/ACCEL switch. The new target speed is stored in the
PCM (the ECM with a diesel engine) when the RES/
ACCEL is released. The PCM also has a 9tap-up9 feature in which vehicle speed increases at a rate of
approximately 2 mph for each momentary switch
activation of the RES/ACCEL switch.
A “tap down” feature is used to decelerate without
disengaging the speed control system. To decelerate
from an existing recorded target speed, momentarily
depress the COAST switch. For each switch activation, speed will be lowered approximately 1 mph.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - VACUUM SUPPLY
TEST
3.7L / 4.7L / 5.9L / 8.0L Gas Powered Engines
3.7L/4.7L/5.9L/8.0L gas powered engines: actual
engine vacuum, a vacuum reservoir, a one-way check
valve and vacuum lines are used to supply vacuum to
the speed control servo.
(1) Disconnect vacuum hose at speed control servo
and install a vacuum gauge into the disconnected
hose.
(2) Start engine and observe gauge at idle. Vacuum gauge should read at least ten inches of mercury.
(3) If vacuum is less than ten inches of mercury,
determine source of leak. Check vacuum line to
engine for leaks. Also check actual engine intake
manifold vacuum. If manifold vacuum does not meet
this requirement, check for poor engine performance
and repair as necessary.
(4) If vacuum line to engine is not leaking, check
for leak at vacuum reservoir. To locate and gain
access to reservoir, refer to Vacuum Reservoir Removal/Installation in this group. Disconnect vacuum line
at reservoir and connect a hand-operated vacuum
pump to reservoir fitting. Apply vacuum. Reservoir
vacuum should not bleed off. If vacuum is being lost,
replace reservoir.
(5) Verify operation of one-way check valve and
check it for leaks.
(a) Locate one-way check valve. The valve is
located in vacuum line between vacuum reservoir
and engine vacuum source. Disconnect vacuum
hoses (lines) at each end of valve.
(b) Connect a hand-operated vacuum pump to
reservoir end of check valve. Apply vacuum. Vacuum should not bleed off. If vacuum is being lost,
replace one-way check valve.
(c) Connect a hand-operated vacuum pump to
vacuum source end of check valve. Apply vacuum.
Vacuum should flow through valve. If vacuum is
not flowing, replace one-way check valve. Seal the
fitting at opposite end of valve with a finger and
apply vacuum. If vacuum will not hold, diaphragm
within check valve has ruptured. Replace valve.
5.7 Gas
Vacuum is not used for any part of the speed con-
trol system if equipped with a 5.7L V-8 engine.
5.9L Diesel Engine With Manual Trans.
Vacuum is not used for any part of the speed con-
trol system if equipped with a diesel engine and a
manual transmission.
DR SPEED CONTROL 8P - 3
SPEED CONTROL (Continued)
5.9L Diesel Engines With Automatic Trans.
If equipped with a diesel powered engine and an
automatic transmission, an electric vacuum pump
and vacuum lines are used to supply vacuum to the
speed control servo. A vacuum reservoir is not used.
DIAGNOSIS AND TESTING - ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speedometer operation should be smooth and without flutter at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control system. The cause of any speedometer problems should
be corrected before proceeding. Refer to Instrument
Cluster for speedometer diagnosis.
If a road test verifies a system problem and the
speedometer operates properly, check for:
• A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
• A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
• Loose, damaged or corroded electrical connections at the servo (if used). Corrosion should be
removed from electrical terminals and a light coating
of Mopar MultiPurpose Grease, or equivalent,
applied.
• Leaking vacuum reservoir (if used).
• Loose or leaking vacuum hoses or connections (if
used).
• Defective one-way vacuum check valve (if used).
• Secure attachment of both ends of the speed con-
trol servo cable (if used).
• Smooth operation of throttle linkage (if used)
and throttle body air valve.
• Failed speed control servo (if used). Do the servo
vacuum test.
CAUTION: When test probing for voltage or continuity at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
SPECIFICATIONS
TORQUE - SPEED CONTROL
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Servo Mounting Bracket-
to-Servo Nuts
Servo Mounting Bracket-
to-Battery Tray Screws
Speed Control Switch
Mounting Screws
Vacuum Reservoir
Mounting Nuts
7-60
4-30
1.7 - 15
3-20
CABLE
DESCRIPTION
The speed control servo cable is connected between
the speed control vacuum servo diaphragm and the
throttle body control linkage. This cable is used with
3.7L/4.7L/5.9L/8.0L gas powered engines only. It is
also used if equipped with a 5.9L diesel engine
equipped with an automatic transmission.
A speed control servo cable is not used if equipped
with either a 5.9L diesel engine equipped with a
manual transmission, or any 5.7L engine/transmission combinations.
OPERATION
This cable causes the throttle control linkage to
open or close the throttle valve in response to movement of the vacuum servo diaphragm.
REMOVAL
3.7L / 4.7L GAS
(1) Disconnect negative battery cable at battery.
(2) Remove air intake tube at top of throttle body.
The accelerator cable must be partially removed to
gain access to speed control cable.
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