DTC U0401: Invalid Data Received From ECM/Pcm A: Description

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The PSCM monitors the HS-CAN messages when the ignition has been on for more than 5 seconds, the voltage to the PSCM is greater than 10 volts and there are no DTCs present inhibiting PSCM operation.

The PCM uses input from several sensors and components to gather vehicle data, then sends this data to the PSCM. If the data is corrupted or invalid, the PCM sends out "invalid", "fault" or "unknown" instead of the actual data. For a list of the messages sent to the PSCM from the PCM, refer to the Network Message List in Description and Operation in the Power Steering article.

DTC U0401:00 (Invalid Data Received from ECM/PCM A: No Sub Type Information) - This DTC sets if the PSCM receives invalid or unknown messages from the PCM instead of valid engine speed, engine state and vehicle speed data messages.