The ECM and skid control ECU communicate with each other via the CAN communication line. If there is a problem in this communication, the ECM sets the DTC.
U0129
DTC Detection Drive Pattern
DTC Detection Condition
Trouble Area
Ignition switch is ON
All of following conditions met for 1 second or more:
Ignition switch ON
+B terminal voltage 8 V or more
No communication between ECM and skid control ECU (1 trip detection logic)
Wire harness (CANL and CANH circuits)
ECM
Skid control ECU
WIRING DIAGRAM
INSPECTION PROCEDURE
Go to CAN communication system for troubleshooting (Click here).
HINT:
When a DTC indicating a CAN communication system malfunction is output, repair the CAN communication system before repairing each corresponding sensor.
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.
If the CAN communication malfunctions, there is no data output from the ECM. In this case, some of the freeze frame data is not correct and not identical to the ECM data. However the ECM data is correct.
