P0687
PPowertrainECM/PCM Power Relay Control Circuit High
What does this code mean?
Severity : MediumP0687 indicates a high voltage on the control circuit of the engine control module power relay. This relay supplies power to the ECM and some components. The module detects that the control circuit is not behaving as expected, for example a relay that stays energised.
Symptoms
- Check engine light on.
- Hard start or no start.
- Battery drains while the vehicle is parked.
- Possible intermittent stalling.
Possible causes
- Faulty or stuck ECM main relay.
- Control circuit shorted to voltage.
- Corroded connector or fuse box terminal.
- Faulty engine control module.
Diagnosis and repair
- Check fuses and battery condition.
- Test the main relay or swap it with an identical known good relay.
- Measure voltage on the control circuit with key on and key off.
- Look for a short in the harness between the ECM and the relay.
- Clear the code and confirm the relay switches off after shutdown.
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Code
P0687
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012