P0670 on GMC
Glow Plug Module Control Circuit
P0670 on GMC vehicles indicates glow plug module control circuit. Au7o has documented this code across 1 GMC model — most commonly on Sierra 3500HD. This code indicates the engine computer detected a fault in the control circuit between the PCM and the glow plug control module on a diesel engine. The glow plug module energizes the glow plugs to preheat the cylinders for cold starting. A fault here mainly causes hard cold starts, rough cold-start running, and white smoke until the engine warms up. Typical repair costs on GMC range from $250 to $1,200, depending on the specific model and root cause.
Common Causes of P0670
- •Faulty glow plug control module
- •Open or shorted wiring between PCM and glow plug module
- •Corroded or loose module connectors
- •Blown fuse feeding the glow plug system
- •Poor ground at the module
- •PCM control circuit fault
P0670 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 P0670 across all makes →Frequently Asked Questions
What does P0670 mean on GMC?▼
P0670 stands for "Glow Plug Module Control Circuit." This code indicates the engine computer detected a fault in the control circuit between the PCM and the glow plug control module on a diesel engine. The glow plug module energizes the glow plugs to preheat the cylinders for cold starting. A fault here mainly causes hard cold starts, rough cold-start running, and white smoke until the engine warms up. On GMC specifically, this code is documented across 1 model.
What causes P0670 on GMC vehicles?▼
Common causes on GMC: Faulty glow plug control module, Open or shorted wiring between PCM and glow plug module, Corroded or loose module connectors, Blown fuse feeding the glow plug system, Poor ground at the module. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0670 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 P0670 documented?▼
Au7o has documented P0670 on 1 GMC model: Sierra 3500HD.