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HOMESERVICE MANUALSHONDA2002CIVIC SIREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 68 (PGM-FI SYSTEM)DTC TROUBLESHOOTINGDTC U0122: F-CAN MALFUNCTION (VSA MODULATOR-CONTROL UNIT-PCM)
2002 Honda Civic Si

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

2002 Honda Civic SiSECTION DTC U0122: F-CAN Malfunction (VSA Modulator-Control Unit-PCM)
WARNING: This page is about a different car, the 2006 Acura MDX, 2005 Acura MDX, 2004 Acura MDX, and 2003 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
  • Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  • If DTC U0073 is stored at the same time as DTC U0122, troubleshoot DTC U0073 first, then recheck for DTC U0122.
  1. Turn the ignition switch ON (II).
  2. Clear the DTC with the HDS.
  3. Check for Temporary DTCs or DTCs with the HDS.

    Is DTC U0122 indicated? 

    1. YES  - Go to step 4.
    2. NO  - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the gauge assembly, the VSA modulator-control unit and the PCM.
  4. Check for a DTC in the DTCs MENU with the HDS.

    Is VSA DTC 86 indicated? 

    1. YES  - Go to step 5.
    2. NO  - Go to step  9.
  5. Turn the ignition switch OFF.
  6. Disconnect the VSA modulator-control unit 47P connector.
  7. Check for continuity between VSA modulator-control unit 47P connector terminals No. 3 and No. 18.
    Fig 1: Checking Continuity Between VSA Modulator-Control Unit 47P Connector Terminals 3 And 18
    G03639806Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step 8.
    2. NO  - Repair open in the wire between the VSA modulator-control unit (No. 3 (No. 18)*) and the PCM (B16 (B15)*), then go to step  14.

      *: CANL line

  8. Check for poor connection at left engine compartment wire harness/dashboard wire harness A 14P connector.

    Is it OK? 

    1. YES  - Substitute a known-good VSA modulator-control unit, then go to step  14 and recheck. If no DTC is indicated, replace the original VSA modulator-control unit, then go to step  14.
    2. NO  - Reconnect the left engine compartment wire harness/dashboard wire harness A 14P connector, then go step  14.
  9. Turn the ignition switch OFF.
  10. Disconnect the VSA modulator-control unit 47P connector.
  11. Turn the ignition switch ON (II).
  12. Measure voltage between VSA modulator-control unit 47P connector terminal No. 38 and body ground.
    Fig 2: Measuring Voltage Between VSA Modulator-Control Unit 47P Connector Terminal 38 And Body Ground
    G03639807Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES  - Go to step 13.
    2. NO  - Check the No. 9 IG METER (10 A) fuse in the driver's under-dash fuse/relay box. If the fuse is OK, repair open in the wire between the No. 10 IG METER (10 A) fuse and the VSA modulator-control unit, then go to step  14.
  13. Check for continuity between VSA modulator-control unit 47P connector terminal No. 32 and body ground.
    Fig 3: Checking Continuity Between VSA Modulator-Control Unit 47P Connector Terminal 32 And Body Ground
    G03639808Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Substitute a known-good VSA modulator-control unit, then go to step 14 and recheck. If no DTC is does not indicated, replace the original VSA modulator-control unit, then go to step 14.
    2. NO  - Repair open in the wire between the VSA modulator-control unit and G302, then go to step 14.
  14. Turn the ignition switch ON (II).
  15. Clear the DTC with the HDS.
  16. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  17. Check for Temporary DTCs or DTCs with the HDS.

    Are any Temporary DTCs or DTCs indicated? 

    1. YES  - If DTC U0122 is indicated, check for poor connections or loose terminals at the gauge assembly, the VSA modulator-control unit and the PCM, then go to step  1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
    2. NO  - Troubleshooting is complete.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.