NAG1 Automatic Transmission

U0401-IMPLAUSIBLE DATA RECEIVED FROM ECM/PCM

For a complete wiring diagram consult Diagrams/Electrical

Theory of Operation


The messages sent on the CAN bus are distinguished by an identifier (ID). Each CAN ID is defined to contain a certain number of bytes. The Transmission Control Module (TCM) verifies that it has received the proper number of bytes for each ID.


- When Monitored:
Continuously with the ignition on, one valid CAN message received at least once, and no U0002-CAN C Bus Off Performance DTC present.

- Set Condition:
When the TCM detects an incorrect CAN message from the Engine Control Module (ECM).







Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. Testing and Inspection


Diagnostic Test


1. CHECK IF FCM CAN BUS DTCS ARE PRESENT
With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTCs present?

Yes


- Diagnose and repair the DTC(s).
- Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test


No


- Go To 2




2. CHECK IF ENGINE DTCS ARE PRESENT
With the scan tool, read Engine DTCs.
Are there any Engine DTCs present?

Yes


- Diagnose and repair the DTC(s).
- Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test


No


- 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. Transmission Control Module - Description
- Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test