Drive, Input From Automatic Transmission

DRIVE, INPUT FROM AUTOMATIC TRANSMISSION

Fault Symptom.
Engine idling speed drops when the selector lever is moved from P or N to another position.

Diagnostic Procedure.
1. Connect the Scan Tool.
Ignition switch in the ON position.
Select READ ON/OFF".
Select "DRIVE".
Check whether an input is present by moving the selector lever from P and N to another position.

If the Scan Tool reading is OK, continue with step 2.
If the Scan Tool reading is not OK, proceed to step 4.

2. Check whether any leakage occurs.
Start the engine and run it at idling speed.
Restrict the flow of air through the Idle Air Control (IAC) valve by squeezing the air hose with a pair of pliers:
- Idling speed should drop substantially.

If idling speed drops, continue with step 3.
If it does not, continue fault diagnosis by checking:
- incorrectly adjusted throttle butterfly
- air leakage (after the butterfly)

Release the constriction.
Idling speed should pick up quickly and after 10-20 seconds then stabilize at its normal 750 rpm when the engine is hot.

If the IAC valve works OK, proceed to step 5.
If it does not, continue with step 3.





3. Check the mechanical interfaces of the IAC valve.
Disconnect the valve's air hoses.
Plug in the valve's electrical connector.
Select "ACTIVATE".
Select "IAC VALVE".
Check visually that the slide rotates freely without any tendency to bind.

If the slide binds or jams, change the IAC valve.
If the value works OK, proceed to step 5.

4. Connect a BOB.
Ignition switch in the ON position.
Measure the voltage across pin 42 and 14:
- In selector lever positions R, D, 3, 2 and 1 the voltage should be about 12 V
- In selector lever positions P and N about 0 V.

If the voltages are OK, continue with step 5.
If the voltages are not OK, check the following:
- the lead between pin 42 of the control module and pin 4 of the selector lever position sensor for continuity/shorting.
- the operation of the selector lever.

5. Drive the car on test to check whether the fault symptoms persist.

If the trouble persists, continue at "Procedure Before ECM Replacement". Component Tests
If the trouble does not persist, the remedial measure taken was correct, otherwise the fault is of intermittent type.