Powertrain
generic / SAE
P0684
Glow Plug Control Module 1 to PCM Communication Range or Performance
Same as P0683 with the communication signals in plausible range yet not matching expected protocol or content.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number6 / 84
Possible causes
- Protocol mismatch high
- Gateway module routing CAN messages incorrectly low
- CAN terminating resistor (120 Ω) drifted out of spec low
Symptoms
- Glow plug warning light on (often orange coil symbol)
- Hard cold start or no start in cold weather
- White smoke from exhaust during warm-up
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 80–400 €
- Estimated time: 0.5–2 h
- Component: glow plug control module 1
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012