P0672: How to Diagnose & Fix — Cylinder 2 Glow Plug Circuit
4 vehicles · 3 makes · $200-$1,800 repair
How to diagnose and fix P0672: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Mercedes-Benz Sprinter · 2007–2025
Sprinter glow plugs fail with age, causing hard starting in cold weather, rough idle when cold, and white smoke on startup. The OM642 V6 is particularly prone to glow plug seizure in the cylinder head, making removal difficult and risking broken glow plugs that require cylinder head removal to extract.
Common Symptoms
- Hard starting in cold weather
- Extended cranking before engine fires
- Rough idle for first 30-60 seconds when cold
- White smoke on startup
- Glow plug warning light staying on
How to Fix
Replace all glow plugs as a set. Apply anti-seize compound to new glow plug threads. On the OM642, use penetrating oil on the glow plugs and allow it to soak before removal to reduce seizure risk. If a glow plug breaks during removal, specialized extraction tools are available before resorting to head removal.
Owner tips & cautions
- TipReplace glow plugs proactively every 80,000 miles before they seize. Apply anti-seize compound generously. A broken glow plug extraction on the OM642 can cost $1,000+ in labor alone.
Chevrolet Silverado 3500HD · 2001–2020
Glow plugs fail causing difficult cold weather starting. Can also swell and break during removal, requiring extraction. Glow plug module can also fail.
Common Symptoms
- Hard starting in cold weather
- Extended cranking
- White smoke on cold start
- Glow plug indicator stays on too long
- Rough idle when cold
How to Fix
Replace failed glow plugs. Use penetrating oil and heat to prevent breakage during removal. Replace glow plug controller module if diagnostics indicate module failure.
Sources for this issue (1)
GMC Sierra 3500HD · 2007–2019
Duramax-equipped Sierra 3500HD owners report hard starting, extended cranking, and rough idle in cold weather due to glow plug system faults. NHTSA complaints and service information commonly involve failed glow plugs, glow plug control module issues, or wiring/connector problems that trigger circuit DTCs and reduce preheat performance.
Common Symptoms
- Hard start or no-start in cold temperatures
- Extended cranking time
- Rough idle and white/gray smoke on startup
- Check Engine light with glow plug circuit codes
- Reduced power briefly after cold start
How to Fix
Scan for glow plug and control module DTCs, load-test the glow plugs, and inspect harness/connectors at the glow plug controller. Replace failed glow plugs and/or the glow plug control module as indicated, then clear codes and verify proper preheat operation. Use OEM glow plugs specified for the engine (LMM/LML/L5P vary by year).
Sources for this issue (1)
Chevrolet Express · 2011–2016
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P0672 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0672 mean?
P0672 stands for "Cylinder 2 Glow Plug Circuit." P0672 is a diesel-engine code indicating a fault in the glow plug circuit for cylinder number 2. Glow plugs heat the combustion chamber to help a diesel engine start, especially in cold weather, and the control module monitors each plug's circuit electrically. When it detects an open, short, or out-of-range condition on the cylinder 2 glow plug circuit, it sets this code. It generally causes hard cold starts, rough running until warm, and possibly white smoke on startup, while the check engine or glow plug light may illuminate.
What are the most common causes of P0672?
The most common causes of P0672 are: Failed (open or shorted) glow plug on cylinder 2, Corroded or loose glow plug connector/terminal, Damaged or broken glow plug wiring/harness, Faulty glow plug control module or relay, High resistance/corrosion at the glow plug bus bar or strap, Poor ground connection in the glow plug circuit, Blown fuse feeding the glow plug circuit. The specific cause varies by vehicle.
How much does it cost to fix P0672?
Repair costs for P0672 range from $200 to $1,800, depending on the vehicle and root cause.
Which vehicles are affected by P0672?
Au7o has documented P0672 across 4 vehicle models from 3 manufacturers: Chevrolet, GMC, Mercedes-Benz.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.