P0673 on GMC
Cylinder 3 Glow Plug Circuit
P0673 on GMC vehicles indicates cylinder 3 glow plug circuit. Au7o has documented this code across 1 GMC model — most commonly on Sierra 3500HD. This is a diesel engine code. Glow plugs heat each cylinder's combustion chamber to make starting easier, particularly in cold conditions. P0673 means the glow plug control system detected an electrical problem in the cylinder 3 glow plug circuit — usually an open circuit, a short, or out-of-range resistance. You'll most likely notice harder cold starts, rough idle while warming up, or extra startup smoke; the glow plug warning light may also illuminate. Typical repair costs on GMC range from $250 to $1,200, depending on the specific model and root cause.
Common Causes of P0673
- •Failed (open or shorted) cylinder 3 glow plug
- •Damaged or corroded glow plug wiring/connector
- •Loose or corroded glow plug terminal/strap
- •Faulty glow plug relay or control module
- •Broken or chafed harness to the glow plug
- •Poor ground or low supply voltage to the circuit
P0673 on GMC by Model
GMC Sierra 3500HD(1 issue)
- Glow plug control module / glow plug circuit faults causing hard cold starts (Duramax)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.
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View P0673 across all makes →Frequently Asked Questions
What does P0673 mean on GMC?▼
P0673 stands for "Cylinder 3 Glow Plug Circuit." This is a diesel engine code. Glow plugs heat each cylinder's combustion chamber to make starting easier, particularly in cold conditions. P0673 means the glow plug control system detected an electrical problem in the cylinder 3 glow plug circuit — usually an open circuit, a short, or out-of-range resistance. You'll most likely notice harder cold starts, rough idle while warming up, or extra startup smoke; the glow plug warning light may also illuminate. On GMC specifically, this code is documented across 1 model.
What causes P0673 on GMC vehicles?▼
Common causes on GMC: Failed (open or shorted) cylinder 3 glow plug, Damaged or corroded glow plug wiring/connector, Loose or corroded glow plug terminal/strap, Faulty glow plug relay or control module, Broken or chafed harness to the glow plug. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0673 on a GMC?▼
Repair costs on GMC range from $250 to $1,200, depending on the specific model and root cause.
Which GMC models have P0673 documented?▼
Au7o has documented P0673 on 1 GMC model: Sierra 3500HD.