Malfunction Indicator Lamp Always On: Description
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The battery positive voltage is supplied directly to the Malfunction Indicator Lamp (MIL). The Engine Control Module (ECM) turns the MIL ON by grounding the MIL control circuit.