P0380 on GMC: How to Diagnose & Fix
Glow Plug/Heater Circuit A Malfunction
1 GMC model · 1 documented issue · $250-$1,200 repair
P0380 on GMC by model: symptoms, diagnosis and fix
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)
P0380 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 P0380 mean on a GMC?
P0380 stands for "Glow Plug/Heater Circuit A Malfunction." P0380 applies to diesel engines and means the computer detected a malfunction in glow plug heater circuit 'A'. Glow plugs preheat the combustion chambers to help a cold diesel start, and the control module monitors the glow plug circuit (often through a relay/control module); when the current or voltage isn't what it expects, it sets this code. The most noticeable symptom is hard cold starting, rough running until warm, or extra white smoke at startup. It indicates an electrical fault in the glow plug system rather than a fuel-injection problem. On GMC it is documented across 1 model: Sierra 3500HD.
What are the most common causes of P0380?
The most common causes of P0380 are: One or more failed glow plugs, Faulty glow plug control module or relay, Corroded or loose glow plug wiring/connectors, Open or shorted glow plug circuit wiring, Blown glow plug fuse, Poor power feed or ground to the glow plug circuit, Failed driver in the engine control module. The specific cause varies by vehicle.
How much does it cost to fix P0380 on a GMC?
Published repair estimates on GMC range from $250 to $1,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0380 on a different make?
View P0380 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.