Drop In Idle Speed

INPUT SIGNAL FROM AUTOMATIC TRANSMISSION





Fault Symptom.
Drop in engine idling speed when the selector lever is moved from P or N.





Basic Requirement.
No diagnostic trouble codes.

Diagnostic Procedure.
1. Check DRIVE performance
- Connect the ISAT Scan Tool.
- Ignition switch in the ON position.
- Select "READ ON/OFF".
- Select "DRIVE".
- Check whether An input signal is present by moving the selector lever from P or N to another position. Does the ISAT scan tool show a correct reading?

YES: Change the idle air control valve and then continue with point 3.
NO: Continue with point 2.





2. Check the DRIVE signal
- Remove the Motronic control module.
- Ignition switch in the ON position.
- Connect the test lamp to pins 69 and 34 of the Motronic control module's connector.
The test lamp should light up when the selector lever is in any position other than P or N.

Test results OK?

YES: Continue with point 3.
NO: Check and if necessary repair or replace the lead between pin 69 of the Motronic control module and pin 4 of the selector lever position switch in the transmission range switch. If the lead is OK, continue fault diagnosis in the Electrical system, wiring diagrams.

3. Final check
- Check whether the DRIVE fault symptom persists.