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
DTC P0685 : PCM Power Control Circuit/Internal Circuit Malfunction
NOTE:
- Before you troubleshoot, review the 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 PCM.
| DTC Description | Confirmed DTC | Pending DTC | Freeze Frame |
|---|---|---|---|
| P0685 PCM Power Control Circuit/Internal Circuit Malfunction |
DTC (PGM-FI)
- Problem verification
-1. Turn the vehicle to the ON mode.
-2. Clear the DTC with the HDS.
-3. Start the engine, and let it idle for 30 seconds.
-4. Turn the vehicle to the OFF (LOCK) mode.
-5. Turn the vehicle to the ON mode.
-6. Check for Pending or Confirmed DTCs with the HDS.
DTC Description Confirmed DTC Pending DTC Freeze Frame P0685 PCM Power Control Circuit/Internal Circuit Malfunction Is DTC P0685 indicated?
YES
The failure is duplicated. Update the PCM if it does not have the latest software, or substitute a known-good PCM , then recheck. If DTC P0685 goes away and the PCM was updated, troubleshooting is complete. If DTC P0685 goes away and the PCM was substituted, replace the original PCM .
NO
Intermittent failure. Check the following items, if the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot :
- PGM-FI main relay 1
- PGM-FI main fuse
- Poor connections or loose terminals between the PCM and the under-hood fuse/relay box
- Poor or loose PCM ground terminals and connections
- Poor or loose 12 volt battery cables and connections
- Check the 12 volt battery
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.