Malfunction Indicator Lamp: Description and Operation

The check engine light will be illuminated if the SMEC receives an incorrect or no signal from certain sensors or emission related systems on California vehicles. This warns the driver that the SMEC has gone into a limp-in mode to keep the system operational.
Each time the ignition is turned on the check engine light will illuminate for 3 seconds as a bulb test. The check engine light can also be used to display trouble codes. Cycle the ignition to on, off, on, off, on within 5 seconds and any fault codes stored in the SMEC will be displayed.