P0689ECM/PCM Power Relay Sense Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The engine module switches its main relay coil to ground (control circuit), reads the switched voltage back on a sense line and keeps the relay on briefly after ignition off to save learned values. P0689 means the sense voltage is too low although the relay is commanded on – the contact does not close or has high resistance, the sense line is open or grounded, or a fuse in the load circuit has blown. GM sets it at 5 V or less with more than 9 V supply in 5 of 6 samples at 1 s, lamp after two trips; GM Europe's V6 below 6 V for 1 s and the 2.0 L turbo below 5 V, both without the lamp. GM includes an open sense line here. Starting problems or stalling follow, and on Saab the throttle control, which uses this voltage, may go into limp mode.
- What you may notice
- Check engine light (depending on the maker)
- Starting problems or no start
- Engine stalls or stumbles
- Possibly electronic throttle limp mode
- Likely causes
- LikelyRelay contact burnt or not closing, relay faulty
- PossibleFuse in the relay load or sense path blown
- PossibleHigh resistance or corrosion in relay carrier, connector or wire
- RareWeak battery
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €10 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.