Engine Error
P0688
ECM/PCM Power Relay Sense Circuit /Open
Severity
High
Symptoms
No start condition, engine stalls suddenly while driving, check engine light
Common Causes
- Blown fuse providing power to the PCM relay
- Defective PCM power relay
- Broken sense wire between relay and PCM
- Short to ground in sensor wiring (e.g., O2 sensor heater short)
How to Fix
- 1 Check and replace related engine fuses
- 2 Replace the PCM relay
- 3 Unplug sensors to locate short circuit
- 4 Repair broken sense wire
Estimated Repair Cost
USD
$20
–
$400
Fuse/Relay: $20 - $50; Short circuit repair: $150 - $400