Diagnostic Strategy

Diagnostic Strategy

Troubleshooting an electronically controlled automatic transmission is simplified by using the proven method of diagnosis. One of the most important things to remember is that there is a definite procedure to follow.

NOTE: Do not take short cuts or assume that critical checks or adjustments have already been made.

Follow the procedures as written to avoid missing critical components or steps.

To correctly diagnose a concern, go to the following information:

- Computers and Control Systems
- On-Line Automotive Service Information System (OASIS)
- TSBs
- Wiring Diagrams

These publications provide the information required when diagnosing transmission concerns.

Use the Diagnostic Flow Chart as a guide and follow the steps as indicated.


Preliminary Inspection

- Know and understand the customer concern.
- Verify the concern by operating the vehicle.
- Check the transmission fluid level and condition.
- Check for non-factory add-on items.
- Check selector lever cable for correct adjustment.
- Check TSBs regarding the concern.


Diagnostics

- Carry out On-Board Diagnostic (OBD) procedures, Key ON Engine OFF (KOEO) and Key ON Engine Running (KOER).
- Record all DTCs.
- Repair all non-transmission codes first.
- Repair all transmission codes second.
- Clear all continuous codes and attempt to repeat them.
- Repair all continuous codes.
- If only pass codes are obtained, go to Diagnosis By Symptom Diagnosis By Symptom for additional information and diagnosis.

Follow the diagnostic sequence to diagnose and repair the concern the first time.