P0690ECM/PCM Power Relay Sense Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- 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. P0690 means the sense voltage is too high: voltage is present although the relay has been off for 2 s – a welded or sticking contact, or external voltage fed in through a short – or, on some systems, overvoltage above 18 V with the relay on. GM sets it at 4 V or more with the relay off, in 50 of 63 samples at 100 ms, lamp after two trips; GM Europe's 2.0 L turbo above 2 V with the relay off or above 18 V with it on, for 2 s, and advises fixing other short-to-voltage codes first. Modules, fans or pumps may keep running after switch-off and the battery drains overnight.
- What you may notice
- Check engine light
- Module, fan or pumps keep running after ignition off
- Battery drains overnight
- Likely causes
- LikelyRelay contact sticking or welded
- PossibleShort to voltage on the sense or load line (external feed from another component)
- PossibleControl wire shorted to ground (relay permanently on)
- RareOvervoltage from the alternator regulator (where the 18 V limit applies)
- 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.