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 any shortcuts or assume that critical checks or adjustments have already been made.

Follow the procedures are written to avoid missing critical components or steps.
To correctly diagnose a concern, have the following available:
- TSBs.
- Wiring Diagram.

These provide the necessary information 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's concern.
- Verify the concern by operating the vehicle.
- Check the fluid levels and condition.
- Check for non-factory add-on items.
- Check shift linkages for correct adjustment.
- Check TSBs regarding the concern.

Diagnostics
- Carry out on-board diagnostic procedures Key On Engine Off (KOEO) and Key On Engine Running (KOER),
- Record all diagnostic trouble codes (DTCs).
- Repair all non-transmission codes first.
- Repair all transmission codes second.
- Erase all continuous codes and attempt to repeat them.
- Repair all continuous codes.
- If only pass codes are obtained, proceed to Diagnosis by Symptom Index for further information and diagnosis. 5R55N

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