U0404

U0404-IMPLAUSIBLE DATA RECEIVED FROM ESM





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 ID received at least once, and no U0002-CAN Bus Off Performance DTC present.
- Set Condition:
When the TCM detects an incorrect CAN ID from the Electronic Shift Module (ESM).

Possible Causes
- FCM CAN BUS DTC S PRESENT
- ELECTRONIC SHIFT MODULE DTC S PRESENT
- TRANSMISSION CONTROL MODULE

Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. Component Tests and General Diagnostics

Diagnostic Test
1. CHECK FOR FCM CAN BUS DTC's
With the scan tool, read FCM DTC's.
Are there any FCM CAN BUS DTC's present?
YES >>Refer to appropriate diagnostic test.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. Transmission Verification Test
NO >>Go To 2

2. ELECTRONIC SHIFT MODULE DTC's PRESENT
With the scan tool, read Electronic Shift Module (ESM) DTC's.
Are there any ESM DTC's present?
YES >>Refer to AUTOMATIC TRANSMISSION and perform the appropriate diagnostic procedure. Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. 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.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. Transmission Verification Test