U0424

U0424-IMPLAUSIBLE DATA RECEIVED FROM HVAC CONTROL MODULE





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 HVAC control module.

Possible Causes
CAN BUS DTC'S PRESENT
HVAC DTC'S PRESENT
TRANSMISSION CONTROL MODULE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test
1. CHECK FOR FCM CAN BUS DTCS
With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTCs present?
Yes >>Refer to Body Control System.
Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test
No >>Go To 2

2. CHECK IF HVAC DTCS ARE PRESENT
With the scan tool, read HVAC DTCs.
Are there any HVAC DTCs present?
Yes >>Refer to HEATING & AIR CONDITIONING - TESTING and perform the appropriate symptom.
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