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 (ECM-VSA Modulator-Control Unit)
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS.
- Check for Temporary DTCs or DTCs with the HDS.
Is DTC U0122 indicated?
YES -Go to step 4.
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.
- Check for DTCs in the DTCs MENU with the HDS.
Is VSA DTC 86 indicated?
YES -Go to step 5.
NO -Go to step 13.
- Turn the ignition switch to LOCK (0).
- Jump the SCS line with the HDS.
- Disconnect the VSA modulator-control unit 47P connector (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ).
- Disconnect ECM connector E (31P).
- Connect VSA modulator-control unit 47P connector terminal No. 11 to body ground with a jumper wire.
- Check for continuity between ECM connector terminal E11 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Go to step 11.
NO -Repair open in the wire between the ECM (E11) and the VSA modulator-control unit, then go to step 13.
- Connect VSA modulator-control unit connector terminal No. 15 to body ground with a jumper wire.
- Check for continuity between ECM connector terminal E24 and body ground.
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 13 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 13.
NO -Repair open in the wire between the ECM (E24) and the VSA modulator-control unit, then go to step 13.
- Reconnect all connectors.
- Turn the ignition switch to ON (II).
- Reset the ECM with the HDS.
- Do the ECM idle learn procedure (see ECM 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 VSA modulator-control unit and the ECM, then go to step 1.
NO -Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's 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.