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DTC codes / P06xx · Computer and output circuits / P0672

P0672Cylinder 2 Glow Plug Circuit

P0672 indicates that the engine control module (ECM) has detected an open circuit or excessive resistance in the glow plug circuit for cylinder 2. This code is specific to diesel engines that use glow plugs to aid cold starting, and it means the ECM is not seeing the expected current flow through that particular glow plug.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illuminated check engine light or glow plug warning lamp
  • Hard starting or rough idle when the engine is cold
  • Excessive white smoke from the exhaust after a cold start
  • Engine misfire or stumbling during the warm-up period
  • Often no symptoms besides the warning light, especially in mild weather

Common causes, most likely first

  1. Faulty glow plug on cylinder 2 (open element or high resistance)
  2. Damaged or corroded electrical connector at the cylinder 2 glow plug
  3. Broken or chafed wiring in the glow plug circuit for cylinder 2
  4. Failed glow plug control module or relay affecting only that circuit
  5. Poor ground connection for the glow plug circuit
  6. ECM internal fault (rare)

How to diagnose and fix it

  1. Inspect the cylinder 2 glow plug connector and wiring for damage, corrosion, or looseness
  2. Measure the resistance of the glow plug with a multimeter and compare to specification
  3. Check for battery voltage at the glow plug connector during the glow plug pre-heat phase
  4. Test the glow plug control module and its relay for proper operation
  5. Replace the faulty glow plug if resistance is out of range
  6. Repair or replace damaged wiring or connectors as needed
  7. Clear the code and verify the repair with a test drive and re-scan

Glow plug circuit checks before replacement

  • A glow plug that tests fine with a multimeter can still fail under load; a current clamp on the feed wire during pre-heat gives a truer picture.
  • Corroded connectors and chafed harness sections near the cylinder head are common culprits that mimic a failed glow plug.
  • The ECM may set P0672 even if the glow plug works, due to a faulty glow plug control module that only affects one channel.
  • Always verify the glow plug part number and voltage rating; incorrect plugs can cause repeat failures and misleading codes.
  • On some vehicles, a weak battery or charging system issue can trigger glow plug circuit codes due to low voltage during pre-heat.

Can I keep driving with P0672?

You can generally continue driving with P0672, but cold starting may be harder and the engine may run rough until warm. Avoid prolonged driving with a known misfire, and address the issue before winter to prevent starting problems.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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