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DTC U0122: F-CAN Malfunction (ECM/PCM-VSA Modulator-Control Unit)

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review GENERAL TROUBLESHOOTING INFORMATION .
  1. Turn the ignition switch to ON (II).
  2. Check for Pending or Confirmed DTCs with the HDS.

    Are DTC U0029 and U0122 Indicated at the same time? 

    YES:  Go to troubleshooting for DTC U0029 (see DTC U0029: F-CAN MALFUNCTION (BUS-OFF (ECM/PCM))  ).

    NO:  Go to step  3.

  3. Clear the DTC with the HDS.
  4. Check for Pending or Confirmed DTCs with the HDS.

    Is DTC U0122 indicated? 

    YES:  Go to step  5.

    NO:  Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the VSA modulator-control unit and the ECM/PCM.

  5. Turn the ignition switch to ON (II), and watch the ABS indicator, the brake system indicator, and the VSA indicator.

    Do the indicators come on and go off? 

    YES:  Go to step  6.

    NO:  Go to symptom troubleshooting for ABS indicator, brake system indicator, and VSA indicator do not go off (see ABS INDICATOR, BRAKE SYSTEM INDICATOR, AND VSA INDICATOR DO NOT GO OFF ).

  6. Turn the ignition switch to LOCK (0).
  7. Jump the SCS line with the HDS.
  8. Disconnect the VSA modulator-control unit 36P connector.
  9. Disconnect ECM/PCM connector A (49P).
  10. Check for continuity between ECM/PCM connector terminal A3 and VSA modulator-control unit 36P connector terminal No. 14.

    Is there continuity? 

    YES:  Go to step  11.

    NO:  Repair open in the wire between the ECM/PCM (A3) and the VSA modulator-control unit, then go to step  12.

    Fig 1: Checking Continuity Between ECM/PCM Connector Terminal A3 & VSA Modulator-Control Unit 36P Connector Terminal No. 14
    G05952937Courtesy of AMERICAN HONDA MOTOR CO., INC.
  11. Check for continuity between ECM/PCM connector terminal A4 and VSA modulator-control unit 36P connector terminal No. 1.

    Is there continuity? 

    YES:  Update the VSA modulator-control unit if it does not have the latest software (see VSA MODULATOR-CONTROL UNIT UPDATE ), or substitute a known-good VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step  12 and recheck. If DTC U0122 is not indicated after substitution, replace the original VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step  12.

    NO:  Repair open in the wire between the ECM/PCM (A4) and the VSA modulator-control unit, then go to step  12.

    Fig 2: Checking Continuity Between ECM/PCM Connector Terminal A4 & VSA Modulator-Control Unit 36P Connector Terminal No. 1
    G05952938Courtesy of AMERICAN HONDA MOTOR CO., INC.
  12. Reconnect all connectors.
  13. Turn the ignition switch to ON (II).
  14. Reset the ECM/PCM with the HDS.
  15. Do ECM/PCM IDLE LEARN PROCEDURE .
  16. Check for Pending or Confirmed DTCs with the HDS.

    Is DTC U0122 indicated? 

    YES:  Check for poor connections or loose terminals at the VSA modulator unit and the ECM/PCM, then go to step  1.

    NO:  Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.

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