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Pinpoint Test F: DTC (Diagnostic Trouble Code) U0121:00

WARNING: This page is about a different car, the 2023 Ford Bronco. However, it is still accessible from the selected car via links, so may be relevant.
  1. Refer to MODULE COMMUNICATION NETWORK for schematic and connector information.

    Normal Operation and Fault Conditions 

    The IPMA communicates with the ABS through the HS-CAN2, GWM and FD-CAN.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    IPMA U0121:00 Lost Communication With Anti-Lock Brake System (ABS) Control Module 'A': No Sub Type Information A continuous memory DTC that sets in the IPMA if messages received from the ABS module over the HS-CAN2 are missing through GWM.

    Possible Sources 

    • Communication network concern
    • ABS module
    • IPMA concern
    • GWM

  2. F1 VERIFY THE CUSTOMER CONCERN

    • Ignition ON.

    • Verify there is an observable symptom present.

    Is there an observable symptom present? 

    Yes  GO to F2 
    No  CLEAR the DTC. The system is operating normally at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

  3. F2 CHECK THE COMMUNICATION NETWORK

    • Using a diagnostic scan tool, perform a network test.

    Does the ABS module pass the network test? 

    Yes  GO to F3 
    No  REFER to: Controller Area Network (CAN) Module Communications Network . REFER to: Ethernet Module Communications Network .

  4. F3 PERFORM THE IPMA (IMAGE PROCESSING MODULE A) SELF-TEST

    • Using a diagnostic scan tool, perform the IPMA self-test.

    Are any non-network Diagnostic Trouble Codes (DTCs) present? 

    Yes  DIAGNOSE all non-network Diagnostic Trouble Codes (DTCs). REFER to Diagnostic Trouble Code (DTC) Chart 
    No  GO to F4 

  5. F4 PERFORM THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE SELF-TEST

    • Using a diagnostic scan tool, perform the ABS module self-test.

    Are any non-network Diagnostic Trouble Codes (DTCs) present? 

    Yes  DIAGNOSE all non-network Diagnostic Trouble Codes (DTCs). REFER to: Anti-Lock Brake System (ABS) and Stability Control .
    No  GO to F5 

  6. F5 PERFORM THE GWM (GATEWAY MODULE A) SELF-TEST

    • Using a diagnostic scan tool, perform the GWM self-test.

    Are any Diagnostic Trouble Codes (DTCs) recorded? 

    Yes  REFER to: Controller Area Network (CAN) Module Communications Network . REFER to: Ethernet Module Communications Network .
    No  GO to F6 

  7. F6 RECHECK THE IPMA (IMAGE PROCESSING MODULE A) DIAGNOSTIC TROUBLE CODES (DTCS)

    • Using a diagnostic scan tool, clear the IPMA Diagnostic Trouble Codes (DTCs).

    • Ignition OFF.

    • Ignition ON.

    • Wait 10 seconds.

    • Using the diagnostic scan tool, perform the continuous memory self-test.

    • Check the IPMA Diagnostic Trouble Codes (DTCs).

    Is DTC U0121:00 still present? 

    Yes  GO to F7 
    No  The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

  8. F7 CHECK FOR OTHER CAUSES OF COMMUNICATION NETWORK CONCERN

    NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the PMI, or the PMI may not have been carried out.

    • CHECK the vehicle service history for recent service actions related to the ABS module or IPMA. If recent service history is found:

      • verify correct replacement module was installed

        • HVBOM may be used to verify correct part fitment

      • verify the configuration of replacement module was correct

        • re-configure module using as-built data if prior configuration is suspect

      • verify the module was not obtained from a like vehicle and installed into customer vehicle

        • return the swapped module to source vehicle and obtain new replacement module

    • Operate the system and determine if the observable symptom is still present.

    Is the observable symptom still present? 

    Yes  GO to F8 
    No  The system is operating correctly at this time. The concern may have been due to incorrect parts replacement procedures or incorrect module configuration.

  9. F8 CHECK FOR CORRECT ABS (ANTI-LOCK BRAKE SYSTEM) MODULE OPERATION

    • Ignition OFF.

    • Disconnect and inspect the ABS module connectors.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary

    • Reconnect the ABS module connectors. Make sure they seat and latch correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, REFER to: Anti-Lock Brake System (ABS) and Stability Control .
    No  The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
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