Transmission Control System

U0401 -IMPLAUSIBLE DATA RECEIVED FROM ECM/PCM





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).

Possible Causes
FCM CAN BUS DTCS
ENGINE DTCS
TRANSMISSION CONTROL MODULE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test
1. CHECK IF FCM CAN BUS DTCS ARE PRESENT
With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTC's present?
Yes >>Refer to Body Control System and diagnose the appropriate symptom.
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 DTC's present?
Yes >>Refer to Computer and Control Systems and diagnose the appropriate symptom(s).
Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test
No >>Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM. Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test