P1789

DIAGNOSTIC TROUBLE CODE P1789
TRANSMISSION RANGE SIGNAL (P, D, 3, 2, 1), DRIVE SIGNAL, OPEN CIRCUIT OR SHORT CIRCUIT TO GROUND

Fault symptom
Disturbances in the car's idling function. No idling compensation

Conditions.
Short circuit to ground or open circuit

Diagnostic procedure
1. Connect ISAT scan tool to the car's data link connector. Check the status of the output signal by initiating DRIVE SIGNAL in the ISAT menu and read the value. The ignition should be ON. ISAT should show OFF with the selector lever in position N.

ISAT should show ON with the selector lever in positions P, D, 3, 2, 1.

If the measurement result is correct, go to step 4.

If the measurement result is wrong, go to step 2.

2. With the ignition switched OFF, connect a BOB between the Transmission Control Module (TCM) and the wiring. Disconnect the connector to the ECM. Switch on the ignition.

Measure the voltage between pins 11 and 35. Nominal value is <0.5 V with the selector lever in position N and 12 V (battery positive voltage) with the selector lever in positions R, D, 3, 2, 1. If the measurement result is wrong, go to step 3.

If the measurement result is correct, go to the ECM system.





3. Carry out continuity measuring of the cable between the transmission and the ECM.

Connect an ohm meter thus:

^ pin 11 (TCM) to pin 47 ECM

Nominal resistance is <1 ohm. If the ohm-meter shows the correct value, go to "Actions Before Changing a TCM".

If the ohm-meter shows the wrong value, check and if necessary, remedy the cable and the connector.

4. Clear the fault code, start and test-drive the car and check if the fault code reappears.

If a fault code is recorded, go to "Actions Before Changing a TCM".