P0689
ECM/PCM Power Relay Sense Circuit Low
ECM power supply
Generic OBD-II
High
What it means
P0689 means the engine computer sees a low voltage on the sense wire it uses to confirm its main power relay is delivering power. Because this relay feeds the ECM itself, a real fault here can cause stalling, hard starting, or a no-start, so it should be diagnosed rather than ignored.
High
Can I keep driving? Risky — this circuit powers the engine computer, so it can cause stalling or a no-start; get it diagnosed before relying on the vehicle.
Common symptoms
What you'll notice
- Check-engine light on
- Engine stalls or is hard to start / no-start
- Intermittent power loss or erratic engine behavior
- Other electrical or sensor codes appearing at the same time
Common causes
Most likely first
- Faulty ECM/PCM main power relayLikely
- Short to ground or low-voltage fault in the sense-circuit wiringCommon
- Corroded or loose connector at the relay or ECMCommon
- Poor battery or ground connection feeding the relayLess often
- Faulty ECM/PCM (least likely)Less often
How to diagnose & fix
Work through it in order
- Read all stored codes and note any companion power, charging, or communication codes.
- Test the ECM power relay and, if possible, swap in an identical known-good relay.
- Check the sense-circuit wiring and connectors for shorts to ground and corrosion.
- Verify battery voltage and the engine/ECM ground connections.
- If the relay and wiring test good, evaluate the ECM/PCM.
FAQ
Quick answers
Is it safe to drive with P0689?+
Not really — this circuit confirms power to the engine computer, so a fault can cause stalling or a no-start at any time. Have it diagnosed promptly.
Can I just clear P0689?+
You can, but if the relay or wiring is faulty the code returns and the car may stall; fix the circuit rather than clearing it.
Related codes
Often seen with P0689
Read & clear P0689 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX