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: Engine Control Module (ECM) Power Control Circuit/Internal Circuit Malfunction: General Description
After the ignition switch is turned off, the engine control module (ECM) does not shut down immediately. After finishing a predetermined process according to the request of each device and system, the power supply is automatically disconnected (self shut-down function). The ECM power is disconnected by controlling PGM-FI main relay 1 (FI MAIN).
During a normal ECM shut down, the shut down process is executed by the CPU, PGM-FI main relay 1 (FI MAIN) is turned off, and the voltage to the ECM is turned off to shut down the ECM. When the voltage to the ECM is turned off and the ECM shuts down without the normal shut down procedure, a malfunction in the PGM-FI main relay 1 (FI MAIN) control circuit is detected and a DTC is stored.
| Execution | Continuous |
| Sequence | None |
| Duration | 1 second or less |
| DTC Type | Two drive cycles, MIL ON |
| OBD Status | N/A |
| Condition | Minimum | Maximum |
|---|---|---|
| Engine speed | 400 rpm | - |
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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.
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