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 P1673 (22): Motor Control Module (MCM) Relay Stays Activated
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
- If the DTC cannot be cleared, do the troubleshooting for DTC U1204 (55).
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS (see DTC CLEAR ).
- Turn the ignition switch to LOCK (0), and wait at least 40 seconds. Turn the ignition switch to ON (II) again.
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1673 (22) indicated?
YES -go to step 5.
NO -Intermittent failure, the system is OK at this time.
- Turn the ignition switch to LOCK (0).
- Turn the battery module switch OFF (see DISCONNECTING THE MOTOR POWER CABLE CONNECTOR FROM THE MOTOR STATOR ).
- Remove the IPU cover (see IPU COVER REMOVAL/INSTALLATION ).
- Remove MCM relay 1 (A).
- Measure the voltage between MCM relay 1 4P connector terminals No. 3 and No. 4.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
When you turn the ignition switch from ON (II) to LOCK(O), does the voltage change from 10 V or more down to 0 V?
YES -go to step 10.
NO -go to step 11.
- Check MCM relay 1 (see
POWER RELAY TEST
).
Is the relay OK?
YES -Repair a short to power in the wire between MCM relay 1 and the MCM (A1), then go to step 14.
NO -Replace MCM relay 1, then go to step 14.
- Remove the PCU lid, the PCU busplate, and the PCU cover (see MOTOR CONTROL MODULE (MCM) REMOVAL/INSTALLATION ).
- Disconnect MCM connector A (31P).
- Check for continuity between body ground and MCM connector terminal A7.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Repair a short to ground in the wire between MCM relay 1 and the MCM (A7), then go to step 14.
NO -go to step 22.
- Reconnect all connectors.
- If removed, reinstall the PCU cover, the PCU busplate, and the PCU lid (see MOTOR CONTROL MODULE (MCM) REMOVAL/INSTALLATION ).
- If removed, reinstall the IPU cover (see IPU COVER REMOVAL/INSTALLATION ), then turn the battery module switch ON (see DISCONNECTING THE MOTOR POWER CABLE CONNECTOR FROM THE MOTOR STATOR ).
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS (see DTC CLEAR ).
- Turn the ignition switch to LOCK (0), and wait at least 40 seconds. Turn the ignition switch to ON (II) again.
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1673 (22) indicated?
YES -go to step 1.
NO -go to step 21.
- Monitor the OBD STATUS for DTC P1673 (22) in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 20, go to the indicated DTC's troubleshooting.
NO -If the screen indicates FAILED, go to step 1. If the screen indicates NOT COMPLETED, go to step 19.
- Reconnect all connectors.
- Reinstall the PCU cover, the PCU busplate, and the PCU lid (see MOTOR CONTROL MODULE (MCM) REMOVAL/INSTALLATION ).
- Reinstall the IPU cover (see IPU COVER REMOVAL/INSTALLATION ), then turn the battery module switch ON (see DISCONNECTING THE MOTOR POWER CABLE CONNECTOR FROM THE MOTOR STATOR ).
- Update the MCM if it does not have the latest software (see MOTOR CONTROL MODULE (MCM) UPDATE ), or substitute a known-good MCM (see SUBSTITUTING THE MCM ).
- Turn the ignition switch to ON (II), and then to LOCK (0), then wait at least 40 seconds. Turn the ignition switch to ON (II) again.
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1673 (22) indicated?
YES -If the MCM was updated, substitute a known-good MCM (see SUBSTITUTING THE MCM ), and recheck. If the MCM was substituted, go to step 1.
NO -go to step 28.
- Monitor the OBD STATUS for DTC P1673 (22) in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -If the MCM was updated, troubleshooting is complete. If the MCM was substituted, replace the original MCM (see MOTOR CONTROL MODULE (MCM) REMOVAL/INSTALLATION ). If any other Pending or Confirmed DTCs were indicated in step 27, go to the indicated DTC's troubleshooting.
NO -
- If the screen indicates FAILED: If the MCM was updated, substitute the MCM (see SUBSTITUTING THE MCM ), and recheck. If the MCM was substituted, go to step 1.
- If the screen indicates NOT COMPLETED: go to step 26.
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.