Key-In Switch.

Fig 1: Identifying Start Control Module (SCU)

Courtesy of VOLVO CARS CORPORATION

The key-in switch is inside the start control module (SCU). When the starter switch is pressed in, it indicates to several systems in the vehicle that the engine is about to be started. A 12V signal is transmitted to the keyless vehicle module (KVM) and central electronic module (CEM).

When the keyless vehicle module (KVM) receives a key-in signal, it activates one of the internal antennas to check that there is a valid key in the passenger compartment. The vehicle cannot be started until the key has been validated.

The start control module (SCU) is powered via the fusebox in the engine compartment.