Design

Design

Alarm
See Design and Function, Alarm.

Central locking
See Design and Function, Central locking.

Immobilizer
See Design and Function, Immobilizer.

Generator (GEN) (Alternator control module (ACM))




See Design and Function, Generator (GEN).

Current limiting
The central electronic module (CEM) checks and sometimes limits the current from the battery and generator.
The central electronic module (CEM) communicates with the alternator control module (ACM) via serial communication.
If there is a fault with current limitation, the general warning lamp will light in the driver information module (DIM) and a text message will be displayed.

Steering wheel module (SWM)




The steering wheel module (SWM) has the task of managing the signals for those functions which can be controlled via the steering wheel control stalks and buttons. The signals are transmitted using LIN communication to the central electronic module (CEM). The central electronic module (CEM) forwards these signals on the controller area network (CAN) to the relevant control modules. The actual functions are not in the steering wheel module (SWM).
The steering wheel module (SWM) manages the control signals for the following functions:
- Volume control and CD track / radio selection
- Volume control during hands free car-phone calls and menu selection for the phone module (PHM)
- Menu selection for traffic information
- Front windshield wipers and washers
- Rear windshield wiper and washer (V70, XC70 and XC90)
- Cruise control
- Turn signal lamps
- High and low beam
- Trip computer and displaying/erasing text messages in the driver information module (DIM).
The steering wheel module (SWM) is integrated into the steering wheel bracket. The steering wheel must be removed to replace the steering wheel module (SWM). Control stalks, key pads and switches can be replaced as separate units.
Cars with DSTC also have a steering wheel angle sensor in the contact reel in the steering wheel module (SWM). For further information, see Design and Function, Steering wheel angle sensor module (SAS).
A simple way to ensure that the steering wheel module (SWM) is powered and grounded is to flash the headlamp high beam or to change the audio or car-phone volume.

Steering wheel buttons




The steering wheel buttons control functions and menu selection for:
- Traffic information (option)
- Audio (option)
- Car phone (option)
- Cruise control (option).
The signals from the steering wheel buttons are transmitted via serial communication.

Headlamps





Warning! The power stage, which is built into the lamp housing, and the wiring for the Bi-Xenon lamps are high voltage.

The headlamps are operated via the light switch module (LSM). This is on the dashboard at the side of the steering wheel. The light switch module (LSM) uses serial communication to communicate with the central electronic module (CEM). Low and high beam are operated by moving the left-hand control stalk towards the steering wheel.
Low beam is powered directly by the central electronic module (CEM). High beam is powered via a directly connected relay in the central electronic module (CEM). The level of the supply voltage to the low beam is regulated by the central electronic module (CEM). When the supply voltage is sufficient (in excess of 13 V), pulse width modulation is used to maintain the voltage level at 13.0 V +/- 0.2 V. This does not apply to cars with Bi-Xenon lamps.
Cars with Bi-Xenon lamps are powered directly via the central electronic module (CEM) without pulse width modulation.
In Bi-Xenon lamps, the reflector in the lamp housing is moved by an actuator motor when changing between high and low beam. The actuator motor is integrated in the lamp housing.
To detect problems with the low beam, the central electronic module (CEM) reads the power consumption of the circuit. If this falls below a certain threshold value a fault will be indicated. The general warning lamp lights in the driver information module (DIM) and a text message is displayed.
There are also diagnostics for the high and low beam function (actuator motor) for Bi-Xenon lamps.
For further information about Bi-Xenon lamps, see Design and Function, Gas discharge lamps (GDL).

Headlamp range adjustment (certain markets)




There are two motors, one on each headlamp, which angle the headlamps upwards or downwards to control the range of the beam. The motors are on the rear of the headlamps.
The motors are controlled by a thumb wheel which is located in the light switch module (LSM) on the dashboard by the side of the steering wheel.
If the thumb wheel is turned, information is transmitted to the motors which adjust the headlamps accordingly.
There are diagnostics for the headlamp range adjustment.

Automatic range adjustment (Bi-Xenon)
There are two motors, one on each headlamp, which angle the headlamps upwards or downwards to control the range of the beam. The motors are on the rear of the headlamps.
The motors are controlled by signals from a position sensor at the rear axle. The sensor detects the angle of the car under different load conditions and sends this information via the rear electronic module (REM) so that the central electronic module (CEM) can determine whether the lamps need to be raised or lowered.
For further information about the inner roof lighting, see Design and Function, rear electronic module (REM).
There are diagnostics for the headlamp range adjustment.

Front fog lamps




If the car has front fog lamps, these are in the bumper casing below the headlamps.
The fog lamps are operated via a button in the light switch module (LSM). An LED in the button lights when the fog lamps are activated. The light switch module (LSM) uses serial communication to communicate with the central electronic module (CEM). The bulbs are powered via a directly connected relay in the central electronic module (CEM).

Front parking lamps




There are a number of lamps positioned around the car to mark its position. These are in the headlamps and tail lamps. The lamps light together with the license plate lighting when the light switch module (LSM) is in parking lamp mode or low beam is on.
The front parking lamps are powered directly via two outputs on the central electronic module (CEM). One of the outputs powers:
- the front left-hand parking lamp
- the left-hand parking lamps.
The other output powers:
- the front right-hand parking lamp
- the right-hand side parking lamps.
The rear parking lamps and license plate lighting are powered by the rear electronic module (REM). For further information, see Design and Function, rear electronic module (REM).
There are diagnostics for the parking lamps.

Turn signal lamps / Hazard warning signal flashers




There are six lamps around the car to indicate direction changes. These are in the headlamps, tail lamps and on the side of the vehicle in front of the doors.
The turn signal lamps are operated using the left-hand control stalk.
To cancel the hazard warning signal flashers, where all the turn signal lights flash, press in the button for the hazard warning signal flasher. This is positioned in the middle of the dashboard by the center air vents.
The front and rear lamps are powered directly from the central electronic module (CEM).
A signal is also sent to the bulb in the hazard warning signal flasher switch when this function is activated.
The central electronic module (CEM) monitors the power consumption on each side to check for bulb faults. If the power consumption falls below a certain threshold value, a fault is indicated and the frequency of the signal to the bulbs is doubled on the side of the blown lamp.
There are diagnostics for the front and rear turn signal lamps.

High level stop lamp




For further information about the high level stop (brake) lamps, see Design and Function, rear electronic module (REM).

Courtesy lighting / key lighting / glove compartment lighting




There are various lamps inside the passenger compartment, such as the courtesy lighting and glove compartment lighting for example. There are also LEDs around the keyhole in the ignition switch.
The lamps for the courtesy lighting are in the soundproofing panels on the driver and passenger sides. The lamp for the glove compartment is positioned on the left-hand inner side.
The lighting time can be programmed via the upper electronic module (UEM). For further information, see Design and Function, upper electronic module (UEM).
There are diagnostics for the key lighting and glove compartment lighting.

Horn




There are two horns in front of the radiator. There are four switches in the steering wheel. The horn is activated when one of these is closed.
The signal continues for as long as the switch is closed.
The horn is also activated when the panic alarm button on the remote control is pressed (certain markets).
The power supply for the horn is controlled from the central electronic module (CEM).

Fuel pump




The fuel pump (FP) is located on the inside of the fuel tank on the right-hand side. The power supply for the pump is checked by the central electronic module (CEM) which operates a relay. This relay controls the power supply to the pump and is directly connected to the central electronic module (CEM).
The central electronic module (CEM) uses the controller area network (CAN) to communicate with the engine control module (ECM) which requests power to the pump system. The active-on-demand pump system that receives a control signal from the engine control module (ECM) to control the flow.
The central electronic module (CEM) also communicates with the supplemental restraint system (SRS) module via a directly connected signal. In the event of a collision, the supplemental restraint system module (SRS) transmits data and the central electronic module (CEM) closes the relay for the pump system and shuts off the power supply to the fuel pump (FP).
There are diagnostics for the input signal from the engine control module (ECM) and for the relay for the fuel pump (FP).
In the event of a fault in the controller area network (CAN) or central electronic module (CEM), there is a limp-home function in the central electronic module (CEM). This keeps the fuel pump (FP) relay active throughout the operating cycle.
This function is stopped in the event of a collision. A signal is transmitted from the supplemental restraint system module (SRS) to the central electronic module (CEM).
If there are electrical faults, the engine cannot be restarted after a collision.

Fuel level (Gasoline/Diesel)




The fuel level in the tank is measured by two sensors. The sensors are located on each side of the fuel tank. Cars with engine B5244S6 have only one sensor, on the pump side. The sensor is directly connected to the central electronic module (CEM).
There are different tables for different fuel tank sizes. The tables are stored in the central electronic module (CEM) and indicate which sensor values correspond to the remaining fuel in the tank. The central electronic module (CEM) determines which tank is in the car by reading a parameter.
The resistance of the sensor increases as the fuel volume in the tank decreases. The signals from the sensors are compared with the values in the fuel tank table to obtain a value for the remaining fuel volume. This data is displayed by the fuel gauge in the driver information module (DIM).
If the sensors are faulty, the fuel gauge will show 0.
There are diagnostics for the fuel level sensors.
The fuel level sensor for Bi-fuel is connected to the rear electronic module (REM). For further information, see Design and Function, rear electronic module (REM).

Washer / wipers




The windshield wipers are powered by a motor positioned under the cowl. There is also a headlamp wiper (S80 and R-models). Other models have high-pressure cleaning. There are also washer nozzles on the hood and bumper cover for cleaning the windshield and headlamps. The washer nozzles are connected to a pump motor on the windshield washer reservoir at the front right of the engine compartment.
For cars with five doors, there is a wiper and washer nozzle for the rear windshield.
The windshield wipers are operated using the right-hand control stalk. There are four positions:
- intermittent
- single sweep
- low speed
- high speed.
The time between strokes for intermittent wiping is adjusted using a ring on the control stalk.
Pull the control stalk towards the steering wheel to clean the windshield. The washer and wipers for the headlamps or high-pressure cleaning system are activated at the same time. The headlamp wipers operate for as long as washing is activated. They are not activated when only the windshield wipers are activated.
Push the control stalk away from the steering wheel to clean the rear windshield. There is a button at the end of the control stalk to control the rear wiper.
Information about the position of the control stalk is transmitted by the steering wheel module (SWM) to the central electronic module (CEM) using serial communication. The central electronic module (CEM) also receives a signal from the wiper motor if the wipers are in the park position.
The central electronic module (CEM) also monitors the windshield washer reservoir level via a level sensor in the reservoir. The switch in the level sensor closes if the level falls below one liter. A text message indicating that the windshield washer fluid needs to be topped up then lights in the driver information module (DIM) for approximately 10 seconds.
The power supply for the rear windshield wiper is via a directly connected relay in the rear electronic module (REM). The windshield wiper motor and high-pressure cleaning are supplied with power via relays in the engine compartment. The washer pump and headlamp wiper motors are powered via the central electronic module (CEM).
There are diagnostics for the windshield wiper motors and relays.

Starter motor




The starter motor is on the left-hand side of the engine by the air cleaner (ACL) housing. The starter motor is powered directly from the battery. There is a solenoid on the starter motor to close the circuit. The central electronic module (CEM) activates a relay in the relay box in the engine compartment to act on the solenoid. This supplies the solenoid with power and closes the circuit for the starter motor.
The starter motor turns when the key is turned to position III in the ignition switch.
There are different functions which prevent starting, depending on whether the car has an automatic or manual transmission. The central electronic module (CEM) also has an electronic immobilizer function which communicates with a transponder in the key. For further information about the immobilizer, see Design and Function, Immobilizer.
- Cars with manual transmissions have a sensor in the clutch pedal. The clutch pedal must be depressed to allow starting (certain markets)
- In cars with type 4T65EV automatic transmissions, a signal is transmitted from the gear-shift position sensor to the transmission control module (TCM) which then sends a directly connected signal to the central electronic module (CEM)
- In cars with AW automatic transmissions, a directly connected signal is transmitted directly from the gear-shift position sensor to the central electronic module (CEM).
There are diagnostics for the relay for the starter motor.

Speed sensitive power steering




If the car has speed dependent power steering to control the steering assistance, there is a solenoid which controls a hydraulic valve on the steering gear.
The solenoid is controlled by the power steering control module. This receives speed data from the directly connected speed signal from the central electronic module (CEM).
The power steering control module uses a signal to check the solenoid. The solenoid deploys the valve on the steering gear to the required degree and regulates the oil in the steering gear to reduce or increase the servo assistance. The steering assistance increases at lower speeds and is reduced at higher speeds.
There are no diagnostics for the power steering.

Additional heater (diesel engines only)





Control of the additional heater on cars with manual climate control (MCC)
The climate control module (CCM) requests that the combustion preheater module (CPM) is started. The central electronic module (CEM) determines whether start is possible. The combustion preheater module (CPM) then receives a signal from the central electronic module (CEM) to start the heater.
Certain conditions must be met before the heater can start. These are:
- Outside temperature below +8 °C (at 12 °C the heater switches off)
- Engine running
- Quantity of fuel greater than 4 liters
- No diagnostic trouble codes (DTCs) that will prevent starting are stored in the central electronic module (CEM)
- The airbags have not deployed.
The heater makes three start attempts. If these fail a diagnostic trouble code (DTC) is stored in the central electronic module (CEM) and a warning message is displayed in the driver information module (DIM). If the conditions change the central electronic module (CEM) requests that the heater is stopped.

Control of the additional heater on cars with electronic climate control (ECC)
The additional heater is controlled by the ECC climate control system as required. In addition to the above conditions, the climate control module (CCM) also takes the outside temperature, engine coolant temperature (ECT) and the temperature selected into account before a request for the heater to start is made.

Parking heater (optional extra)




The start time of the heater is programmed as follows:
- the desired parking function is selected by turning the ring on the control stalk
- the desired time is selected by turning the ring on the control stalk
- press the RESET button.
Direct start can also be used to start the heater.
The climate control module (CCM) is activated when the engine coolant temperature (ECT) is greater than +20 °C. The blower fan starts and distributes the air in the passenger compartment.
Certain conditions must be met before the heater can start. These are:
- Quantity of fuel greater than 4 liters
- No diagnostic trouble codes (DTCs) that will prevent starting are stored in the central electronic module (CEM)
- The airbags have not deployed.
When the conditions are met, the heater glow plug is activated for 1 minute. If the voltage has dropped below 11.5 V, the climate control module (CCM) is switched off. The heater and the climate control module (CCM) are stopped if the voltage falls below 11.3 V. A message indicating low battery voltage is displayed in the driver information module (DIM). These voltage values apply even if the heater is operating normally.
To minimize the risk of the fuel pump for the heater failing due to lack of use, the central electronic module (CEM) sends a signal every week to the combustion preheater module (CPM) to activate the pump for approximately 1 second. This takes place when the ignition is switched off.

Twilight sensor




The twilight sensor consists of a photo diode powered from the central electronic module (CEM). The conductivity of the diode depends on the amount of light to which it is exposed.
The diode is under a diffusing lens which reduces the sensitivity of the photo diode to the angle of the light hitting it. Increased light intensity reduces the voltage over the photo diode.
The control module measures the voltage across the photo diode and converts the voltage to information which is then transmitted to other control modules via the controller area network (CAN).
The twilight sensor is in the same holder as the sun sensor.
There are diagnostics for the twilight sensor.

Sun sensor (electronic climate control only)




The sun sensor consists of a photo diode powered from the central electronic module (CEM). The conductivity of the diode depends on the amount of light to which it is exposed.
The diode is located under a diffusing lens which reduces the sensitivity of the photo diode to the angle of the light hitting it. Increased sun intensity reduces the voltage over the photodiode.
The control module measures the voltage across the photo diode and converts the voltage to information which is then transmitted to the climate control module (CCM) via the controller area network (CAN).
The sun sensor is located in the middle of the dashboard by the windshield.
For further information, see Design and Function, climate control module (CCM).
There are diagnostics for the sun sensor.

Blind spot information system (BLIS)




The blind spot information system (BLIS) is an auxiliary system designed to help the vehicle's driver when moving sideways. The blind spot information system (BLIS) consists of two cameras integrated in the external rear view mirrors and two LEDs located in the panel at the front of the inside of the respective windows.
The central electronic module (CEM) communicates with the left camera module (LCM) and the right camera module (RCM) via serial communication.
The blind spot information system (BLIS) is always activated automatically when the ignition is switched on, but it is possible to deactivate and activate the blind spot information system (BLIS) using one of the switches on the dashboard environment panel on the climate control module (CCM). A signal is then transmitted via the central electronic module (CEM) to the left camera module (LCM) and the right camera module (RCM) with a request to deactivate or activate the blind spot information system (BLIS).
When reverse gear is engaged, the blind spot information system (BLIS) is deactivated.
The blind spot information system (BLIS) can be diagnosed.