ECM or PCM Power Relay Sense Circuit High
Same as P0689 with the sense line shorted to supply or showing higher voltage than expected. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Affected components
- Ecm power relay
Common causes
- High likelihood: Sense line shorted to supply
- Low likelihood: Connector pins corroded - high contact resistance
- Low likelihood: Supply wire pinched against B+ source
Possible symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.