System Overview

Central Electronic Module (CEM)

System Overview

Control Module







The central electronic module (CEM) controls the Controller area network (CAN) and acts as a bridge between the high and low speed networks and the data link connector (DLC). It also manages the following functions:
- Alarm (certain functions)
- Locks (certain functions)
- Immobilizer
- Headlamps
- Parking lights/license plate lighting
- Front fog lamps
- Headlamp range adjustment (certain markets)
- Automatic range adjustment (Bi-Xenon)
- Turn signal lamps
- High-mounted stop lamp
- Courtesy lighting/key lighting/glove compartment lighting
- Rear window lift mechanisms
- Fuel pump
- Wiper/washers for the windshield and headlamps
- Starter motor
- Speed sensitive power steering
- Electrically heated seats
- Horn.

The control module is installed as a separate unit in a relay box under the soundproofing panel on the driver's side. The control module is removed from the relay box for replacement.

The car configuration file is stored in the central electronic module (CEM). It contains information about the car VIN number, structure week and the equipment in the car. When replacing the central electronic module (CEM), the VIN cannot be read off until the software has been downloaded from the Volvo central database.

The central electronic module (CEM) communicates with components which are directly connected and also with other control modules and components via serial communication and the control area network (CAN).

The control module checks activations and input and output signals using an integrated diagnostic system A diagnostic trouble code (DTC) is stored if the control module detects an error. In certain cases the central electronic module (CEM) replaces the faulty signal with a substitute signal. Other control modules also communicate on the network with the central electronic module (CEM) if they have diagnostic trouble codes (DTCs) stored. This function is used when reading off diagnostic trouble codes (DTCs) without VADIS/VIDA.

Any diagnostic trouble codes (DTCs) are stored in the control module memory. This information can be read off using VADIS/VIDA via the data link connector (DLC) in the car.

The easiest way to check if the central electronic module (CEM) is grounded and receiving power is to activate the hazard warning signal flasher. The central electronic module (CEM) is supplied with power if the function operates. Another way of checking that the central electronic module (CEM) is supplied with voltage and grounded is to activate one of the rear window lift mechanisms.

Signals



















The above tables summarizes the input signals to and the output signals from the central electronic module (CEM). The signal types are divided into directly connected signals, serial communication and Controller area network (CAN) communication. The illustration displays the same information with the Volvo component designations.