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. 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 properly diagnose a concern the technician should have the following publications available:

• This Service Manual
• Transmission Reference Manual
• Powertrain Control/Emissions Diagnosis (PC/ED) Manual
• OASIS Messages
• Technical Service Bulletins (TSBs)
• Electrical and Vacuum Troubleshooting Manual (EVTM)

These publications provide the information required when diagnosing transmission concerns.

Using the Diagnostic Flow Chart as a guide, follow the steps as indicated.

Preliminary Inspection

• Know and understand the customer's concern.
• Check the fluid level and condition.
• Verify the concern by operating the vehicle.
• Check for nonfactory add-on items.
• Check shift linkages for proper adjustment.
• Check TSBs and OASIS messages for the concern.

Diagnostics

• Perform On-Board Diagnostic Procedures (KOEO, KOER).
• Record all Diagnostic Trouble Codes (DTCs).
• Repair all nontransmission codes FIRST.
• Repair all transmission codes SECOND.
• Erase all continuous codes and attempt to repeat them.
• Repair all continuous codes.
• If ONLY PASS codes, proceed to Diagnosis by Symptom Index under Diagnosis by Symptom in the Diagnosis and Testing portion of this section for further information and diagnosis.

By following the diagnostic sequence, the service technician will be able to diagnose and repair the concern the first time.