Initial Inspection

STANDARD PROCEDURE

NAG1-PRE DIAGNOSTIC TROUBLESHOOTING PROCEDURE
For the Transmission circuit diagram, refer to Wiring Diagram Information.

1. Low fluid level can be the cause of many transmission problems. If the fluid level is low, locate and repair the leak then check and adjust the fluid level in accordance with the Service Information.
Always perform diagnostics with a fully charged battery to avoid false symptoms.
With the scan tool, read the engine DTCs. Check and repair all engine DTCs prior to performing transmission symptom diagnostic procedures.
With the scan tool, read and record all Transmission DTCs.

NOTE: If the TCM detects and stores a DTC, the TCM also stores the vehicles operating conditions under which the DTC originally set and is located in scan tool under Environmental Data. Before erasing any stored DTCs, record any available data to assist in duplicating the conditions in which the DTC originally set.

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Check connectors - Clean/repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all diagnostic monitors have run. Verify flash level of transmission controller. Some problems are corrected by software upgrades to the transmission controller. Verify no variant DTCs are present. If variant DTCs are present, perform their respective test first.
If the TCM (EGS) is flashed, perform a EGS initialization with the scan tool to relearn variant coding.
Check for any Service Information Tune-ups or Service Bulletins that may apply.

NOTE: Were there any repairs that fixed the customer's complaint?

Yes >> Testing complete.
No >> Refer to AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS category and perform the appropriate symptom.