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 to ON (II).
- Check for Pending or Confirmed DTCs with the HDS.
Are DTC U0029 and U0122 indicated at the same time?
YES -Go to the troubleshooting for DTC U0029 (see DTC U0029: F-CAN MALFUNCTION (BUS-OFF (PCM)) ).
NO -Go to step 3.
- Clear the DTC with the HDS.
- 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 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 VSA symptom troubleshooting for an ABS indicator, brake system indicator, and VSA indicator that will not go off (see SYMPTOM TROUBLESHOOTING INDEX ).
- Turn the ignition switch to LOCK (0).
- Jump the SCS line with the HDS.
- Disconnect the VSA modulator-control unit 47P connector.
- Disconnect PCM connector A (44P).
- Check for continuity between PCM connector terminal A36 and VSA modulator-control unit 47P connector terminal No. 12.Fig 1: Checking Continuity Between PCM Connector Terminal A36 And VSA Modulator-Control Unit 47P Connector Terminal No. 12
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Go to step 11.
NO -Repair an open in the wire between the PCM (A36) and the VSA modulator-control unit, then go to step 12.
- Check for continuity between PCM connector terminal A37 and VSA modulator-control unit 47P connector terminal No. 13.Fig 2: Checking Continuity Between PCM Connector Terminal A37 And VSA Modulator-Control Unit 47P Connector Terminal No. 13
Courtesy of AMERICAN HONDA MOTOR CO., INC.
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 an open in the wire between the PCM (A37) and the VSA modulator-control unit, then go to step 12.
- Reconnect all connectors.
- Turn the ignition switch to ON (II).
- Reset the PCM with the HDS.
- Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC U0122 indicated?
YES -Check for poor connections or loose terminals at the gauge control module, the VSA modulator-control unit, and the 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.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.