Checking The Speed Control Operation - DaimlerChrysler Jeep Grand Cherokee 2002 Service Manual

Symptom:

*CHECKING THE SPEED CONTROL OPERATION

BRAKE SWITCH SIGNAL
ECM DTC(S) PRESENT
ENGINE CONTROL MODULE
SPEED CONTROL SWITCHES
VSS SIGNAL
INTERMITTENT CONDITION
TEST
1 Turn the ignition on.
With the DRBIII , read the ECM DTCs.
Are there any ECM DTCs present?
Yes → Refer to symptom list for problems related to the ECM DTC.
→ Go To 2
No
2 Start the engine.
With the DRBIII , read the S/C SWITCH VOLTS.
Observe the S/C Switch volts on the DRBIII 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?
Yes → Go To 3
→ Refer to symptom list for problems related to S/C Switches.
No
3 Test drive the vehicle above 60 km/h (35 MPH).
Attempt to Set the Speed Control.
Does the Speed Control function properly?
Yes → Test Complete.
→ Go To 4
No
4 Turn the ignition on.
With the DRBIII in Sensors, read Vehicle Speed.
Have an assistant drive the vehicle while you are observing the Vehicle Speed on the
DRBIII .
While observing vehicle speed on the DRBIII , note any rapid changes (signal
dropouts) in the reading that do not correspond with actual vehicle speed.
Is the DRBIII displaying an accurate vehicle speed?
Yes → Go To 5
→ Refer to symptom list for problems related to the Vehicle Speed
No
POSSIBLE CAUSES
ACTION
Perform SPEED CONTROL VERIFICATION - VER-4.
Perform SPEED CONTROL VERIFICATION - VER-4.
Sensor.
Perform SPEED CONTROL VERIFICATION - VER-4.
DRIVEABILITY - DIESEL
227
APPLICABILITY
All
All
All
All