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 P0685: PCM Power Control Circuit/Internal Circuit Malfunction
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
- If the problem doesn't return after you clear the DTC, or it this DTC is stored intermittently, check for loose terminals at the IGP line connectors before replacing the PCM.
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS.
- Start the engine, and let it idle for 30 seconds.
- Turn the ignition switch to LOCK (0).
- Start the engine, and let it idle for 30 seconds.
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II).
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0685 indicated?
YES -Go to step 9.
NO -Intermittent failure, the system is OK at this time.
- Update the PCM if it does not have the latest software (see PCM Update ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
- Start the engine, and let it idle for 30 seconds.
- Turn the ignition switch to LOCK (0).
- Start the engine, and let it idle for 30 seconds.
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II).
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0685 indicated?
YES -If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step 10. If the PCM was substituted, go to step 1.
NO -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ). If any other Pending or Confirmed 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.