Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC U0122: F-CAN Malfunction (PCM-VSA Modulator-Control Unit)
- Turn the ignition switch ON (II).
- Check for Temporary DTCs or DTCs with the HDS.
Are DTC U0028 and U0122 indicated at the same time?
YES - Go to troubleshooting for DTC U0028.
NO - Go to step 3.
- Clear the DTC with the HDS.
- Check for Temporary DTCs or 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 gauge control module, the VSA modulator-control unit, and the PCM.
- Check for communication to the VSA system with the HDS.
Does the HDS communicate with the VSA modulator-control unit?
YES - Go to step 6.
NO - Go to the DLC circuit troubleshooting .
- Turn the ignition switch OFF.
- Jump the SCS line with the HDS.
- Disconnect the VSA modulator-control unit 46P connector.
- Disconnect PCM connector A (44P).
- Check for continuity between PCM connector terminal A48 and VSA modulator-control unit 46P connector terminal No. 39.Fig 1: Identifying Continuity Between PCM Connector Terminal A48 And VSA Modulator-Control Unit Connector Terminal 39
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES - Go to step 11.
NO - Repair open in the wire between the PCM (A48) and the VSA modulator-control unit, then go to step 12.
- Check for continuity between PCM connector terminal A49 and VSA modulator-control unit 46P connector terminal No. 38.Fig 2: Identifying Continuity Between PCM Connector Terminal A49 And VSA Modulator-Control Unit Connector Terminal 38
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES - 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, 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 PCM (A49) and the VSA modulator-control unit, then go to step 12.
- Reconnect all connectors.
- Turn the ignition switch ON (II).
- Reset the PCM with the HDS.
- Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
- Check for Temporary DTCs or DTCs with the HDS.
Is DTC U0122 indicated?
YES - Check for poor connections or loose terminals at the gauge control module, the VSA modulator unit, and the PCM, then go to step 1.
NO - Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTCs troubleshooting.
NO RELATED
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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.