U1509

U1509-IMPLAUSIBLE ENGINE VARIANT MESSAGE DATA LENGTH RECEIVED





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 ECM/PCM.

Possible Causes
FCM CAN BUS DTC'S PRESENT
ECM/PCM 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 DTC's present?
Yes >>Refer to Body Control System and perform the appropriate symptom(s).
Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test
No >>Go To 2

2. CHECK IF ECM/PCM DTCS ARE PRESENT
With the scan tool, read ECM/PCM DTCs.
Are there any ECM/PCM DTCs present?
Yes >>Refer to Computer and Control Systems 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