Cylinder 1 Glow Plug Circuit Malfunction
Glow plug control module isn't seeing the right current draw on cylinder 1's glow plug circuit.
What it means (plain English)
Diesels use glow plugs to preheat the combustion chamber for cold starts. The glow plug control module fires each plug and monitors current draw. If a plug is open (burnt out), shorted, or the wire is broken, you get P067X — last digit = cylinder number. Symptom is hard cold starting and white smoke on a cold start.
What the computer is actually seeing
Glow plug controller measured current outside expected range when energizing cylinder 1's plug.
What a healthy reading looks like
Glow plug cold resistance: typically 0.5–1.5 Ω. Current draw per plug: 8–20 A during preheat depending on system voltage.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Measure resistance of each glow plug to ground. Open = bad.
- 2Inspect the harness / bus bar for breaks and corrosion.
- 3Verify the control module is sending voltage to each plug for the right duration.
- 4WARNING: Glow plugs can seize. Use heat, penetrant, and patience. Snapping one off costs head removal.
Common causes
- Burnt out glow plug (open circuit)
- Broken / corroded glow plug bus bar or harness
- Failed glow plug control module
- Seized glow plug (broke off in head — careful removing)
Typical repair cost
$200 (one plug + R&R) to $3,000+ (broken plug, head removal).
Related codes
Frequently asked questions
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