2006 Chevy Duramax LLY Glow Plug Error P0671-P0678: Cold Start Issue and Diagnosis

Model: 2006 Chevy Duramax LLY Fault Code: P2177 Posted: 2021-02-12 17:31

I'm looking for help with my 2006 Chevrolet Silverado 2500HD equipped with the 6.6L Duramax LLY engine. The truck is throwing diagnostic codes P0671 through P0078, indicating a fault in all eight glow plug circuits. The vehicle starts and runs smoothly even in extremely cold conditions (down to 0°F), which suggests that the glow plugs themselves are functional. When I clear the codes using an OBD2 scanner, the Check Engine Light (CEL) turns off and remains off while the engine is warm. However, on subsequent cold starts, the CEL reactivates. This behavior makes me suspect a potential issue with the glow plug control module or its wiring harness. Any insights, troubleshooting steps, or recommendations for diagnosing this specific P0671-P0678 error in a 2006 Duramax LLY would be greatly appreciated.