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DTC code

P0684

Glow Plug Control Module 1 to PCM Communication Circuit Range/Performance

Technical guide

reference โ€” not individually verified

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

Probable causes

  • high: Protocol mismatch
  • low: Gateway module routing CAN messages incorrectly
  • low: CAN terminating resistor (120 ฮฉ) 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 โ€” 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 โ€œunknownโ€. It never suggests a diagnosis โ€” 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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P0684 โ€” Glow Plug Control Module 1 to PCM Communication Circuit Range/Performance โ€” CodMec