CHECK ENGINE Indicator Lamp

CHECK ENGINE indicator lamp

Schematic:

The CHECK ENGINE lamp (MIL) warns the driver when a fault occurs in the engine management system.

The lamp is powered from the main instrument unit and grounded internally by the main instrument unit. The engine control module continuously sends the bus information CHECK ENGINE, unit ON/OFF.

On receiving CHECK ENGINE ON, the control module grounds the output of the lamp which then lights up.

In certain markets, the TCM (transmission control module) lights the CHECK ENGINE lamp.

If the engine control module changes status on the message to CHECK ENGINE OFF, the light goes out.

On ignition ON, the lamp comes on until the engine starts; if there is no fault, the engine control module sends the bus information CHECK ENGINE OFF and the lamp goes out.

Diagnostics
The function has its own diagnostics in the sending system.