DTC code
P0684
Glow Plug Control Module 1 to PCM Communication Circuit Range/Performance
Technical guide
reference — not individually verifiedSymptoms
- 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
Probable causes
- high: Protocol mismatch
- low: Gateway module routing CAN messages incorrectly
- low: CAN terminating resistor (120 Ω) drifted out of spec
Diagnostic steps
Check the components involved: glow plug control module 1. Verify wiring and connectors before replacing any part. Job difficulty: medium (workshop equipment required). Typical European range — 80-400 EUR, 0.5-2 h. Reference values only.
Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.
AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.
0 confirmed cases on P0684
Nothing confirmed yet for this code. No guess is offered on purpose.
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