NAG1 Automatic Transmission

NAG1 PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE

For a complete wiring diagram Refer to Diagrams/Electrical Electrical Diagrams


Perform the following pre-diagnostic troubleshooting procedures prior to performing any diagnostic test.


NOTE: Low fluid level can be the cause of many transmission problems. Visually inspect the transmission and cooler lines for leakage and repair as necessary and adjust the fluid level. If no visual leaks are observed and the vehicle has obtained over 1610 km (1000 miles) from either new or transmission service, a fluid level check is unnecessary.

Always perform diagnostics with a fully charged battery to avoid false symptoms.

1. With the scan tool, read the engine DTCs. Check and repair all engine DTCs prior to performing transmission symptom diagnostic procedures.
2. 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, it is recommended to record any available data to assist in duplicating the conditions in which the DTC originally set.

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


Did any of the above procedures repair the vehicle?

Yes

- Testing is complete.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Refer to the identified category and perform the appropriate symptom(s).