MIL Circuit: Description
WARNING: This page is about a different car, the 2006 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunction detections by the ECM. By turning the ignition switch on (IG), power is supplied to the MIL circuit, and the ECM provides the circuit ground, which illuminates the MIL.
The MIL operation can be checked visually: When the ignition switch is first turned on (IG), the MIL should be illuminated and should then turn off. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the intelligent tester.