Malfunction Indicator Light
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.
As a bulb and system check, the MIL will illuminate when ignition switch is turned to ON position and engine is not running. When engine is started, MIL should go out. If MIL does not go out, a malfunction has been detected in the computerized engine control system or MIL circuit is faulty. MIL may be used on some models to display a stored DTC. To access DTCs, see SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article.