Diagnostics

Diagnostics





Diagnosing an electronically controlled automatic transmission is simplified by using the following procedures. One of the most important things to remember is that there is a definite procedure to follow. DO NOT TAKE SHORTCUTS OR ASSUME THAT CRITICAL CHECKS OR ADJUSTMENTS HAVE ALREADY BEEN MADE. Follow the procedures as written to avoid missing critical components or steps. By following the diagnostic sequence, the technician will be able to diagnose and repair the concern the first time.

On-Board Diagnostic (OBD) with Scan Tool

These self-tests should be used to diagnose the PCM and should be carried out in order.

NOTE: Make sure to use the latest scan tool software release.

1. If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).

NOTE: The Vehicle Communication Module (VCM) LED prove-out confirms power and ground from the DLC (Data Link Connector) to the VCM (Vehicle Communication Module).

2. If the scan tool does not communicate with the VCM (Vehicle Communication Module) :
- check the VCM (Vehicle Communication Module) connection to the vehicle.

- check the scan tool connection to the VCM (Vehicle Communication Module).

- refer to Information Bus to diagnose no power to the scan tool.


3. If the scan tool does not communicate with the vehicle:
- verify the ignition is in the RUN position.

- verify scan tool operation with a known good vehicle.

- refer to Information Bus to diagnose no response from the PCM.


4. Carry out the network test.
- If the scan tool responds with no communication from one or more modules, refer to Information Bus.

- If the network test passes, retrieve and record the continuous memory DTCs.


5. Clear the continuous DTCs and carry out the PCM self-test.

6. If DTCs retrieved are related to the concern, GO to the DTC Chart. External Controls

7. If no DTCs related to the concern are retrieved, GO to Diagnosis By Symptom Diagnosis By Symptom.