Ignition Switch: Description and Operation

Ignition Switch







The ignition switch powers certain functions in the engine control module (ECM) via fuses in the front integrated relay/fusebox and central electronic module (CEM). The ignition switch also supplies the engine control module (ECM) with signals such as:
- "wake up" signal
- start signal.

"Wake Up" signal
The ignition switch transmits a high signal (U(bat)) to the engine control module (ECM) via the central electronic module (CEM) indicating that the ignition switch is in position I or II. The system prepares for start-up (for example by temporarily activating the fuel pump (FP) relay).

Start signal
The ignition switch transmits a high signal (U(bat)) to the engine control module (ECM) when the ignition switch is in position III.

The engine control module (ECM) activates the starter motor relay. The relay in turn activates the starter motor.

The fuse in the front integrated relay/fusebox supplies current to the ignition switch. The central electronic module (CEM) has diagnostics for the ignition switch.