P1636

P1636-TCM INTERNAL- EXTERNAL WATCHDOG PERFORMANCE





Theory of Operation
The Transmission Control Module (TCM) performs various internal tests to verify proper controller operation. This DTC indicates that watch dog circuitry external to the microprocessor has detected an error. If the TCM watch dog circuitry external to the microprocessor detects an error, the controller will enter Limp-in mode and illuminate the MIL.
- When Monitored:
Continuously with the ignition on.
- Set Condition:
If the TCM watch dog circuitry external to the microprocessor detects an error.

Possible Causes
- TRANSMISSION CONTROL MODULE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. NAG1 Automatic Transmission

Diagnostic Test
1. TRANSMISSION CONTROL MODULE
View repair
Repair
Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM. Refer to Body Control Systems for diagnostic procedures and for further possible causes. Testing and Inspection
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. NAG1 Transmission Verification Test