The check engine light comes on each time the ignition key is turned ON and stays on for a few seconds as a bulb test. If the engine controller receives an incorrect signal or no signal from either the coolant temperature sensor, charge temperature sensor, manifold absolute pressure sensor, throttle position sensor, battery voltage sensor input or emission related system on California vehicles the check engine light on the instrument panel is illuminated.
This is a warning that the engine controller has gone into Limp In Mode in an attempt to keep the system operational. Cycle the ignition switch ON , OFF , ON , OFF , ON , within 5 seconds and any fault codes stored in the memory will be displayed. For more details on fault codes, please refer to Driveability & Emissions Controls .
Limp In Mode is the attempt by the engine controller to compensate for the failure of certain components by substituting information from other sources.