Code result
P0686
ECM/PCM Power Relay Control Circuit Low
Moderate severity
What it means
The control circuit for the ECM main power relay is open. Without this relay, the controller cannot maintain its keep-alive supply.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Main relay defective
highOne of the most commonly reported causes for this code — check this first.
Relay control wire open
mediumA plausible cause — test and verify before replacing parts.
Pin pushed back out of connector body
lowLess common, but worth ruling out after the more likely causes.
Related help
Get the full diagnosis
Add your vehicle and see step-by-step repair help, recalls, and TSBs in Wrenchify.
Diagnose P0686 freeNo credit card required