Code result
P0684
Glow Plug Control Module 1 to PCM Communication Range or Performance
Moderate severity
What it means
Same as P0683 with the communication signals in plausible range yet not matching expected protocol or content.
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
Protocol mismatch
highOne of the most commonly reported causes for this code — check this first.
Gateway module routing CAN messages incorrectly
lowLess common, but worth ruling out after the more likely causes.
CAN terminating resistor (120 Ω) drifted out of spec
lowLess common, but worth ruling out after the more likely causes.
Related help
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