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Home >> Volvo >> 2010 >> V50 T5 AWD L5-2.5L Turbo VIN 67 B5254T7 >> Repair and Diagnosis >> Body and Frame >> Body Control Systems >> Description and Operation >> Central Electronic Module (CEM) >> Functions >> Part 1

Part 1






Function

Alarm
See Design and Function, Alarm.

Locks
See Design and Function, Central locking.

Immobilizer
See Design and Function, Immobilizer/start inhibition.

Alcolock (option 2009-)
See Design and Function, Alcohol Analyzing Start Inhibitor.

Automatic start/stop of engine (2010-)
See Design and Function, Automatic start/stop of engine (2010-, only on vehicles with the function automatic start/stop of engine)

Alternator




See Design and Function, Generator (GEN) and Design and Function, Engine control module (ECM).
See also Design and Function, Regenerating brake energy (2010-).

Current limiting




Central electronic module (CEM) (4/56) communicates with the engine control module (ECM) (4/46) on the controller area network (CAN) The engine control module (ECM) communicates with alternator control module (ACM) (4/98). In this way the central electronic module (CEM) receives information about how much current the generator produces and how much current can be used for the various loads in the vehicle.
Under certain conditions the generator cannot produce enough current for those loads which are connected. The central electronic module (CEM) communicate with the with climate control module (CCM) (3/112) which then completely or partially switches off the following loads.
- electrical additional heater
- rear demist
- electrically heated seats
- heated door mirrors.
The central electronic module (CEM) also transmits a request via the Control area network (CAN) to the engine control module (ECM) to increase the engine idle speed.
When the engine is not running all current is taken from the battery. There are a number of different loads which can be activated when the engine is not running. For example the infotainment system. The central electronic module (CEM) continuously monitors the voltage level of the battery. When the voltage level is too low the central electronic module (CEM) transmits information to the infotainment control module (ICM) (16/1) which then shuts off the infotainment system. In the event of a fault, the central electronic module (CEM) transmits data via the Control area network (CAN) to the driver information module (DIM) (5/1) which displays a text message to the user.
If the infotainment system used in key position II, when the engine is not running, the information is sent to the driver information module (DIM). A message is displayed if the infotainment system is switched off for 2 minutes.
See also Design and Function, Activating automatic start/stop of engine (2010-, only on vehicles with the function automatic start/stop of engine)

Charge voltage




To charge the battery optimally the central electronic module (CEM) calculates the output voltage from the generator (GEN) using the temperature of the battery. The alternator control module (ACM) controls the output voltage, depending on the control from the central electronic module (CEM). See the illustration above. In some driving conditions for example, the engine control module (ECM) is able to affect generator (GEN) control, whereby the output voltage will deviate from the above.
See also Design and Function, Regenerating brake energy (2010-).

Headlamps




Depending on the position of the knob in the light switch module (LSM) (3/111), the module transmits a request to the central electronic module (CEM) to switch on low beam. Central electronic module (CEM) (4/56) supplies power to the low beam directly via an output.
The level of the supply voltage to the low beam is controlled using pulse width modulation of the central electronic module (CEM). This means that the average value of the voltage level to the low beam does not exceed 13.2 V, despite the fact that the supply voltage may be higher.
To change to high beam, the left-hand control stalk (3/133) is pulled towards the steering wheel. The control area network (CAN) signal from the steering wheel module (SWM) (3/254) is transmitted to the central electronic module (CEM) which activates the high beam relay (2/63) and supplies power to the high beam. For Bi-Xenon lamps, the position of the reflector is also changed so that the Xenon lamp is on at high beam.
The central electronic module (CEM) also transmits a CAN signal to the driver information module (DIM) (5/1) to light the indicator lamp for high beam.
There is a Limp Home function which ensures that low beam still works if there is a fault in the control area network (CAN). For Bi-Xenon lamps the beam is then set to the shortest range.
For more information about Bi-Xenon lights, see Design and Function, GDL-lights/Design and Function, Headlamp Control Module (HCM) (S40/V50 2008-).

For more information on Bi-Xenon lights:
S40/V50:
See: Design and Function - GDL-lights (-200719).
See: Design and Function, Headlamp Control Module (HCM) (200720-).
C30/C70:
See: Design and Function, GDL-lights (-200945).
See: Design and Function, Headlamp Control Module (HCM) (200946-).

Parking lights / number plate lighting




The parking lamps (10/11-12, 10/44-45 and 10/51-52) and license plate lighting (10/3) lights when:
- the knob in the light switch module (LSM) (3/111) is in the low beam position
- the knob in the light switch module (LSM) is in the parking lamp position
- low beam is lit via the low beam automatic function (market dependent).
The central electronic module (CEM) (4/56) receives information from the light switch module (LSM) which is directly connected to activate the lamps.
The lamps are powered directly via two outputs on the central electronic module (CEM).
The license plate lighting, front parking lamp on the left-hand side and the rear parking lamp on the right hand side are supplied with power from one output. The front parking lamp on the right-hand side and the rear parking lamp on the left hand side are supplied with power from the other output in the Central Electronic Module (CEM).
To detect problems with the lamp faults, the central electronic module (CEM) reads the power consumption of each output.
The parking lamps have a limp Home function and will work even if there is a fault in the control area network (CAN) or an open-circuit in the serial communication between the light switch module (LSM) and the central electronic module (CEM). The parking lamps will function when the ignition key is in position II.

Headlamp range adjustment




Headlamp range adjustment is controlled by the light switch module (LSM) (3/111) which is directly connected to the actuator motors.
If the thumb wheel in the lamp switch module is turned, information about the position of the wheel is transmitted to the actuator motors. The actuator motors change the angle of the reflectors in the headlamps. The headlamp range can be adjusted in 16 stages.

Automatic range adjustment (Bi-Xenon)
S40/V50:
See: Design and Function - GDL-lights (-200719).
See: Design and Function, Headlamp Control Module (HCM) (200720-).
C30/C70:
See: Design and Function, GDL-lights (-200945).
See: Design and Function, Headlamp Control Module (HCM) (200946-).

Front fog lamps (certain lamps)




The front fog lamps (10/5-6) are activated by pressing the button for the front fog lamps in the light switch module (LSM) (3/111). The light switch module (LSM) is directly connected to the central electronic module (CEM) (4/56).
The power supply for the lamps is via a directly connected relay (2/34) on the central electronic module (CEM).

Turn signal lamps / Hazard warning signal flashers




This function is controlled by the left control stalk (3/133). The steering wheel module (SWM) (3/254) sends signals via the control area network (CAN) to the central electronic module (CEM) (4/56) to activate the turn signal lamps (10/13-14 and 10/47-54).
To activate the indicator for the turn signal lamp and to supply the turn signal lamp with voltage directly via one output, the central electronic module (CEM) transmits information to:
- driver information module (DIM) (5/1)
- driver door module (DDM) (3/126)
- passenger door module (PDM) (3/127)
- trailer module (TRM).
The turn signal lamps in the door mirrors are supplied with voltage via the driver door module (DDM) or the passenger door module (PDM).
If a trailer or similar is connected the symbol for a trailer in the driver information module (DIM) will be activated in time with the indicator light for the turn signal lamp.
The power supply is pulsed and the turn signal lamps are activated 90 times per minute.
The hazard warning signal flasher is activated by closing the switch (3/6) and transmits a signal to the central electronic module (CEM) to start the function. The central electronic module (CEM) transmits a signal in the same way as when activating the turn signal lamp, but to both sides. The central electronic module (CEM) also transmits a signal to the bulb in the switch to indicate that the hazard warning signal flashers are on.
If the ignition key is in position I or II, there is a clicking sound from the driver information module (DIM). If the ignition is switched off, there is no sound, but the hazard warning signal flashers continue to flash.
If a fault occurs with a lamp, the central electronic module (CEM) detects the reduction in power consumption and the frequency is doubled on the side where the fault occurred. The display in the driver information module (DIM) will occur at twice the frequency.

High level stop lamp




When the stop lamp switch (3/9) is closed, a signal is transmitted to the central electronic module (CEM) (4/56). The high mounted stop brake lamp (10/19) is supplied with power directly from the central electronic module (CEM). The stop lamp is supplied with power for as long as the stop lamp switch is closed.

Courtesy lighting/sun visor/glove compartment lighting




The interior roof lighting front (10/22) and rear (10/150) a total of four lamps is activated by the relevant switch.
The inner roof lighting and courtesy lighting (10/97-102) is automatically activated when a door is opened, when unlocking using the remote control or when activating the approach lighting.
In order for the automatic activation to function the light switch in the roof console must be in the auto position. This only applies to roof lighting. The courtesy lighting is activated regardless of the position of the light switch.
The interior roof lighting and the courtesy lighting is powered by the central electronic module (CEM) via the relay for courtesy lighting (2/89). The interior roof lighting and the courtesy lighting can be dimmed when the central electronic module (CEM) activates/ deactivates general lighting. This is because the return cable from the interior roof lighting to the Central Electronic Module (CEM) can be controlled.
Courtesy lighting activated:
- when the request for courtesy and roof lighting is transmitted from the remote receiver to the central electronic module (CEM) using serial communication
- when the remote control receiver has received a command to unlock from one of the remote controls
- when one of the doors is opened.
The lighting in the sun visors (10/114-115) and the lighting in the glove compartment (10/29) is powered by the central electronic module (CEM) via the relay for courtesy lighting (2/89). The lighting in the sun visor is activated when the cover for the vanity mirror is opened. The lighting in the glove compartment is activated when the cover for the glove compartment is opened.

Cargo compartment lighting




The cargo compartment lighting is activated when the trunk lid is opened. When the trunk lid opens the switch in the trunk lid lock unit (3/78) is activated.
The lighting (4 door 10/24, 5 door 10/25) is powered by the central electronic module (CEM) (4/56) via the relay for courtesy lighting (2/89).

Horn




The horn (16/10-11) is operated when the steering wheel module (SWM) (3/254) receives a signal from the switches in the steering wheel. The steering wheel module (SWM) transmits information via a directly connected cable to the central electronic module (CEM)(4/56) indicating that the switch is closed. The central electronic module (CEM) activates the relay (2/17) for power supply to the horn.

Fuel pump




The central electronic module (CEM) (4/56) receives a request from the engine control module (ECM) (4/46) via the control area network (CAN) to start the fuel pump (FP). The central electronic module (CEM) then activates the relay (2/23) which supplies the fuel pump unit (4/83) with power, which in turn powers the fuel pump (FP) (6/33).
If the controller area network (CAN) does not function the relay for the power supply to the fuel pump control module will not be activated.
In the event of a collision in which the airbags are deployed, a signal is transmitted from the supplemental restraint system (SRS) module (4/9) via the control area network (CAN) to the central electronic module (CEM). The central electronic module (CEM) deactivates the relay for the fuel pump unit.

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