Glow Plug System Diagnosis: Description
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The glow plug system is used to assist in providing the heat required to begin combustion during engine starting at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as during the engine operation. The ECM controls glow plug ON times by monitoring coolant temperatures and glow plug voltage. This system check will check the glow plugs and glow plug feed circuit coming from the relay/controller.