DaimlerChrysler Jeep Grand Cherokee 2002, Service Manual

Page: 235 / 284

Symptom:
*CHECKING THE SPEED CONTROL OPERATION
POSSIBLE CAUSES
BRAKE SWITCH SIGNAL
ECM DTC(S) PRESENT
ENGINE CONTROL MODULE
SPEED CONTROL SWITCHES
VSS SIGNAL
INTERMITTENT CONDITION
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIII
t
, read the ECM DTCs.
Are there any ECM DTCs present?
All
Yes
→
Refer to symptom list for problems related to the ECM DTC.
Perform SPEED CONTROL VERIFICATION - VER-4.
No
→
Go To 2
2 Start the engine.
With the DRBIII
t
, read the S/C SWITCH VOLTS.
Observe the S/C Switch volts on the DRBIII
t
while pressing and holding each S/C
Switch button separately.
NOTE: Pressing each S/C Switch button should result in the following
voltages: ON/OFF 0.55v - 1.15, SET 3.0 - 3.6v, RESUME/ACCEL 3.9 - 4.2v,
CANCEL 1.2 - 2.05v, COAST 2.2 - 2.95v, No Button Pressed 4.4 - 4.7v
Does each switch provide the correct voltage?
All
Yes
→
Go To 3
No
→
Refer to symptom list for problems related to S/C Switches.
Perform SPEED CONTROL VERIFICATION - VER-4.
3 Test drive the vehicle above 60 km/h (35 MPH).
Attempt to Set the Speed Control.
Does the Speed Control function properly? All
Yes
→
Test Complete.
No
→
Go To 4
4 Turn the ignition on.
With the DRBIII
t
in Sensors, read Vehicle Speed.
Have an assistant drive the vehicle while you are observing the Vehicle Speed on the
DRBIII
t
.
While observing vehicle speed on the DRBIII
t
, note any rapid changes (signal
dropouts) in the reading that do not correspond with actual vehicle speed.
Is the DRBIII
t
displaying an accurate vehicle speed?
All
Yes
→
Go To 5
No
→
Refer to symptom list for problems related to the Vehicle Speed
Sensor.
Perform SPEED CONTROL VERIFICATION - VER-4.
227
DRIVEABILITY - DIESEL
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