Engine Speed Dipping, Drive

Fault Symptom
Engine idling speed drops when selector lever moved from P or N.

Conditions
Shorting to ground or open circuit.





Procedure
1. Check the transmission control module's output signal

- Connect the ISAT scan tool.
- Turn the ignition switch to the ON position.
- Select "READ ON/OFF".
- Select "DRIVE". The ISAT scan tool should show OFF with the selector lever in positions P and N, and ON with it in positions R, D, 3, 2 and 1.

Are the readings correct?

YES: Proceed to point 4.
NO: Continue with, point 2.

2. Check the engine management system's input signal

- Unplug the connector from the engine management system's control module.
- Turn the ignition switch-to the ON position.
- Connect a test lamp to the connector as follows:
M4.1: to pins 86 and 58
M5.2: to pins 69 and 54
Saab Trionic: to pins 14 and 60.
The test lamp should light up when the selector lever is in the P and N positions and remain off in the other positions.

Is the signal OK?

YES: Continue fault diagnosis in the Engine management system. Then proceed to point 4.
NO: Continue with point 3.





3. Check The Wiring
Check the continuity of the wiring between pin 11 of the transmission control module and pin 86 (M4.1), pin 69 (M5.2) or pin 14 (Saab Trionic) of the engine management system control module.

Is the wiring OK?

YES: Continue with point 4.
NO: Rectify the fault and continue with point 4.

4. Final check

Start the engine, move the selector lever to position D and check whether the fault symptom persists.

Does the fault symptom persist?

YES: Continue as described under "Before Changing A Control Module". Before Changing A Control Module
NO: The remedial action taken was correct or the fault is of an intermittent nature.