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: ECM/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 if this DTC is stored intermittently, check for loose terminals at the IGP line connectors before replacing the ECM/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 ECM/PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/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 ECM/PCM was updated, substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step 10. If the ECM/PCM was substituted, go to step 1.
NO -If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/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.