Pinpoint Test As: PSCM (Power Steering Control Module) DTC (Diagnostic Trouble Code) U0401 Invalid Data Received From Powertrain Control Module

Normal Operation and Fault Conditions

Description
The PSCM monitors the HS-CAN messages when the voltage to the PSCM is greater than 10 volts and there are no Diagnostic Trouble Codes (DTCs) present inhibiting PSCM operation.
For additional information on the messages sent to the PSCM from the PCM module, REFER to: Power Steering - System Operation and Component Description .

Pinpoint Test Applicability
This test applies to PSCM DTC U0401 Invalid Data Received from the PCM only. It does not apply to any other module except the PSCM.

DTC Diagnostic Strategy
If the module DTC list results in a large number of Diagnostic Trouble Codes (DTCs), diagnose all module hard faults first (C102D, C1B00, C200B, C200C, C200D, U2011 and U3000) before diagnosing any network faults (lost communication or invalid data). If voltage concern Diagnostic Trouble Codes (DTCs) are present, diagnose those after any module hard faults and before any network faults. Diagnose all current and active Diagnostic Trouble Codes (DTCs) before diagnosing any historic Diagnostic Trouble Codes (DTCs).

Pinpoint Test Purpose
To direct the diagnosis to the module and associated circuit sending the faulty or unknown information in the messages.

Diagnostic Aids
DTC U0401:00 indicates a concern with the PCM. The module reporting this DTC is not the problem module. Do not install a new PSCM as part of the repair for PSCM DTC U0401:00.
When this DTC is set, steering assist is reduced resulting in higher steering efforts during low speed maneuvers.

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
PSCM U0401:00	Invalid Data Received from ECM/PCM A: No Sub Type Information	The DTC sets when the PSCM receives invalid data from the PCM. The data is likely invalid due to PCM internal errors, damaged or inoperative sensors or components the PCM uses to gather vehicle data. The invalid data DTC is not set due to the PSCM, PSCM wiring or connectors.

Possible Sources