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Pinpoint Test Aa: PSCM (Power Steering Control Module) DTC (Diagnostic Trouble Code) U0100:00 Lost Communication With ECM / Pcm "A"

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
  1. NOTE: Refer to Steering GSB for additional connector and wiring inspection tips.

    Refer to Wiring Diagrams POWER STEERING CONTROLS for schematic and connector information.

    Normal Operation and Fault Conditions 

    Description 

    • 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 Diagnostic Trouble Codes (DTCs) present inhibiting PSCM operation.
    • For additional information on the messages sent to the PSCM from the PCM, REFER to: Power Steering - System Operation and Component Description .

    Pinpoint Test Applicability 

    • This test applies to PSCMDTC U0100 Lost Communication with 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 verify the PSCM wiring harness and connectors are OK. This test checks the connectors and wiring from the PSCM 3 pin connector at the steering gear to the in-line connector in the engine compartment. If these circuits are working correctly, the test then directs to check the PCM and wiring harness.

    Diagnostic Aids 

    • Do not install a new PSCM as part of the repair for a PSCMDTC U0100:00.
    • DTC U0100:00 indicates a possible failure of the HS-CAN which can be due to a circuit fault in the HS-CAN, the PSCM wiring harness or a PCM concern.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    PSCM U0100:00 Lost Communication With ECM/PCM "A": No Sub Type Information This DTC sets when the PSCM does not receive the PCM messages within a certain time frame. This can occur if the PCM wiring harness or electrical connectors are loose or damaged, or if the vehicle battery state of charge levels are low.

    Possible Sources 

    • Fuse(s)
    • Wiring, terminals or connectors
    • PCM

  2. NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

  3. COMPLETE THE FDRS GUIDED ROUTINE

    1. NOTE: This procedure must be completed using FDRS. Do not clear DTCs until the FDRS procedure has completed.To complete the diagnosis, navigate to the FDRS Guided Routine tab and carry out the procedure 

      Electronic Power Assist Steering (EPAS) Communication Error

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