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Pinpoint Test J: U0100, U0401: Notes

Normal Operation and Fault Conditions 

With the ignition ON, the PCM sends messages to the ABS module over the HS-CAN. If the ABS module does not receive these messages within the specified time frame, the ABS module sets DTCs. This can be due to a PCM failure, a circuit failure on the HS-CAN or an excessive load on the network. For information on the messages sent to the ABS module by the PCM, Anti-Lock Control .

DTC Fault Trigger Conditions 

DTC Description Fault Trigger Conditions
U0100 Lost Communication with ECM / PCM This DTC sets in continuous memory if the ABS module does not receive any messages from the PCM.
U0401 Invalid Data Received From ECM / PCM A This DTC sets in continuous memory if any one of the following messages is "invalid" instead of the actual information; accelerator pedal position, brake pedal applied, cruise control status, engine RPM, selector lever (PRNDL) status or transmission shift in progress.

Possible Causes