P0690 code meaning
ECM/PCM Power Relay Sense Circuit High
Powertrain system Generic code P06xx codes Check engine light
What P0690 means
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.
P0690 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0690
- Check engine light
- Module, fan or pumps keep running after ignition off
- Battery drains overnight
Common causes of P0690
- Most 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)
- Less likelyOvervoltage from the alternator regulator (where the 18 V limit applies)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ECM power relayRelay control circuitEngine control module
What each part of P0690 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 90 | The exact fault in that area. |
What to do next
- Note P0690 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0690
What does P0690 mean?
P0690 means "ECM/PCM Power Relay Sense Circuit High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0690?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0690 fail an emissions test?
Yes, it can. P0690 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0690 to fix?
Difficulty: easy. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0690 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.