Central Electronic Module (CEM)

Fig 1: CEM

Courtesy of VOLVO CARS OF NORTH AMERICA.

The central electronic module (CEM) (4/56) is the master unit for the immobilizer function. The central electronic module (CEM) and engine control module (ECM) are linked to each other through codes. The central electronic module (CEM) is also programmed with a code for each ignition key for the vehicle.

The central electronic module (CEM) transmits commands and signals to the other units in the system. The central electronic module (CEM) also approves the identity of the key. The key is checked via the antenna ring. The antenna ring is installed around the ignition switch. There is a transponder (communication circuit) in the ignition key. The identification code of the transponder is unique. The code must be learned by the central electronic module (CEM) before the key can be used to start the vehicle. This code is learned during installation at the factory. New keys can be added afterwards.

The central electronic module (CEM) controls the relay for the fuel pump and the relay for the starter motor (not applicable to B8444S).

For further information about the central electronic module (CEM), see Design and Function, central electronic module (CEM).