Engine Error
P0685
ECM/PCM Power Relay Control Circuit /Open
Severity
High
Symptoms
Engine cranks but will not start, no communication with OBD2 scanner
Common Causes
- Failed PCM power relay
- Blown main PCM fuse
- Open circuit in the relay control wire
- Dead battery or bad ground
How to Fix
- 1 Test and replace PCM power relay
- 2 Replace blown fuses and check for shorts
- 3 Trace and repair control wiring
- 4 Clean chassis ground connections
Estimated Repair Cost
USD
$20
–
$250
Relay or fuse: $20 - $50; Wiring diagnostic: $150