Central Electronic Module (CEM)

Central Electronic Module (CEM)

Diagnostic functions

General
The control module has a built-in diagnostic system, the Volvo on-board diagnostic (OBD) system. This system continuously monitors itself and the input and output signals.

Diagnostic trouble codes (DTCs)
The control module will store a diagnostic trouble code (DTC) if it detects a fault. The control module can store 20 diagnostic trouble codes (DTCs).
If a fault disappears for any reason after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

Reading off the Volvo on-board diagnostic (OBD) system
Fault data and other information can be read off using the VADIS/VIDA PC which is connected to the data link connector (DLC) via VCT 2000 under the center console cover. The VADIS/VIDA PC communicates with the control module via a standardized interface.

Volvo on-board diagnostic (OBD) system
With the VADIS/VIDA PC it is possible to:
- read off and erase stored diagnostic trouble codes (DTCs).
- activate components/functions according to certain predetermined patterns
- continuously monitor the values and status of input and output signals
- read off the control module identification.
- program and read off the programmed values.
The following conditions must be met before the Volvo on-board diagnostic (OBD) system is activated:
- the ignition must be on
- the battery voltage must be normal.

Reading and erasing diagnostic trouble codes (DTCs)
Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.
The on-board diagnostic (OBD) system can identify 20 different faults in the form of diagnostic trouble codes (DTCs). Diagnostic trouble codes (DTCs) can only be erased when all diagnostic trouble codes (DTCs) have been read at least once.

Activating components/functions
This function allows the system components/functions to be activated individually. The ignition must be on for activation to be possible.
The following components and functions can be activated:
- high beam
- low beam
- parking lamps
- rear fog lamps
- front fog lamps
- bulb failure warning sensor
- instrument lighting
- windshield wipers
- tail lamps / side marker lamps
- tailgate wiper
For further information about activation, see Description of activation.

Reading off input and output signals
Using this function, the values and status of the control module input and output signals can be continuously read off.
The following parameters can be read off:
- the switch for high beam flash, input signal
- lighting switch, input signal
- high / low beam switch, input signal
- high beam, high beam warning lamp and the socket for auxiliary lamps, output signal
- low beam, output signal
- parking lamps, output signal
- tail lamps / side marker lamps, output signal
- rheostat turn angle
- lighting in the combined instrument panel, info center, cigarette lighter etc.
- switch for front fog lamps, input signal
- front fog lamps, output signal
- switch for the rear fog lamp, input signal
- rear fog lamp, output signal
- stop (brake) light switch, input signal
- back-up (reversing) lamp switch, input signal
- warning lamp for the bulb failure warning sensor, output signal
- intermittent wiper switch in the windshield wiper lever, input signal
- parking position switch in the windshield wiper motor, input signal
- windshield wiper motor via the windshield wiper lever, output signal
- switch for the windshield washer, input signal
- switch for the tailgate wiper, input signal
- tailgate wiper motor, output signal
- switch for the tailgate washer, input signal
- ignition switch position, input signal
- battery voltage. 15/2-supply from the ignition switch
- speed signal
For further information about parameters, see Description of parameters.

Reading off the control module identification
The VADIS/VIDA PC identifies control modules by reading a code from the memory of the module. This code contains information about the control module P/N and the current software version.

Programming and reading off the programmed values, central electronic module (CEM)
With this option, the data in the control module can be programmed and read off. The aim of programming is to adapt the system to the type of body, market requirements and the equipment level.
All these functions are dealt with via VADIS/VIDA vehicle communication.

Programming automatic low beam
This parameter determines whether low beam should be on when the ignition is switched on and the lighting switch is in position 0.
This function is market dependent. Contact the dealer if you are not sure about this function. Unless otherwise stated, automatic low beam is standard for the USA.

Programming twin headlamps
This parameter indicates if the car is equipped with twin headlamps (separate headlamp inserts for high and low beam) or not
NOTE: If the car is equipped with separate headlamp inserts for high and low beam, low beam will be lit when high beam or high beam flash is activated.

Programming the front fog lamps
This parameter indicates whether the car is equipped with front fog lamps or not.
NOTE: The parameter must be programmed when installing after market fog lamps.

Programming the tailgate wiper
This parameter indicates whether the car is equipped with a tailgate wiper or not.

Programming the tailgate wiper when reversing
This parameter indicates whether the tailgate wiper starts when back-up (reverse) gear is selected or not.
NOTE: The tailgate wiper only starts if the windshield wipers are activated.

Reading off the follow-me-home lights
This parameter indicates how long the follow-me-homes should light.
NOTE: The parameter can only be read. It cannot be programmed.