Function
Function
Alarm
See Design and Function, Alarm.
Central locking
See Design and Function, Central locking.
Sunroof operation
The sun roof module (SRM) (4/33) communicates with the upper electronic module (UEM) (4/70) using serial communication.
Information about the sun roof position and information to be used for diagnosis is sent from the sun roof module (SRM) to the upper electronic module (UEM). The information about the position is transmitted on to other control modules, such as the climate control module (CCM) (3/112) via the central electronic module (CEM) (4/56).
The communication between the upper electronic module (UEM) and the sun roof module (SRM) mainly consists of diagnostic information.
For further information, see Design and Function, Sun roof.
Rain sensor module (RSM)
The rain sensor module (RSM) (7/149) determines whether there is water on the windshield. The sensor assesses the volume of water on the windshield and the prevailing exterior light conditions. This information is then sent, via the upper electronic module (4/70), to other control modules in the car on the controller area network (CAN). These control modules in turn ensure that the windshield wipers are set to the correct speed. The rain sensor senses if the windshield is dirty or covered with traffic film and automatically compensates accordingly. The rain sensor also senses heavier splashes on the windshield. The windshield wipers are then operated at top speed.
The rain sensor module (RSM) communicate with the upper electronic module (UEM) using serial communication. Power is supplied from the upper electronic module (UEM) via the power supply signal EXT.X, when the ignition key is in positions I or II. The rain sensor is active for 10 minutes after the ignition has been switched off.
The steering wheel module (SWM) (3/254) transmits a signal about the position of the windshield wiper stalk via LIN-communication to the central electronic module (CEM) (4/56). The central electronic module (CEM) sends this information onwards on the controller area network (CAN) to the upper electronic module (UEM). If the stalk is moved to the intermittent wiping/rain sensor position, the upper electronic module (UEM) transmits this data to the rain sensor module (RSM) which is then activated.
The rain sensor module (RSM) sends information via the upper electronic module (UEM) to the central electronic module (CEM) which then deploys the wiper motor. The sensitivity can be adjusted using the collar on the wiper stalk.
If a fault occurs in the rain sensor module (RSM), the upper electronic module (UEM) transmits an error message to the central electronic module (CEM). If there is a fault message when the rain sensor is active, the central electronic module (CEM) selects top speed for the windshield wipers until the windshield wiper stalk is moved from the intermittent/rain sensor position. If the fault recurs, intermittent wiping will be activated when the wiper stalk is next moved to the intermittent/rain sensor position, although only at a fixed interval.
Interior roof lighting
The interior roof lighting and reading lamps, front (3/117) and rear (10/150) are controlled via the upper electronic module (UEM) (4/70) in that they are supplied with voltage directly from the control module when each switch is activated. The courtesy lighting is also activated when the doors are opened or when approach lighting is activated.
Data is sent to the upper electronic module (UEM) from the rear electronic module (REM) (4/58) via the controller area network (CAN). This data indicates which doors or tailgate/trunk lid are opened or closed.
The request for keyhole lighting, courtesy lighting and cargo compartment lighting is sent from the upper electronic module (UEM) to the central electronic module (CEM) (4/56) and rear electrical module (REM) via the controller area network (CAN).
The cargo compartment lighting in the V70 and XC70 (10/25) is powered by the upper electronic module (UEM). The lamp is activated if the upper electronic module (UEM) receives information from the rear electronic module (REM) indicating that the tailgate is open.
The sun visor lighting (10/114-115) is powered by the upper electronic module (UEM) using the voltage supply signal EXT.X. The lamp is activated when the flap covering the mirror in the sun visor is opened.
Automatic rear view mirror anti-dazzle
The upper electronic module (UEM) receives data from two photo sensors, one on the front and one on the reverse of the rear view mirror. If the upper electronic module (UEM) determines that the anti-dazzle function is required, a signal is sent to the electro-chromatic mirror which diffuses to the level requested.
The signal transfer occurs internally in the rear view mirror, and is carried out directly between the upper electronic module (UEM) and the anti-dazzle function.
Note! The rear view mirror with automatic anti-dazzle can only be installed in the factory. Upgrading to, or removing an anti-dazzle rear view mirror cannot be carried out after market due to software limitations.
Seat belt reminder
The seat belt reminder is activated when the upper electronic module (UEM) (4/70) receives a signal from the supplemental restraint system module (SRS) (4/9), via the controller area network (CAN), which indicates that the seat belt is not engaged despite someone sitting in the front seat.
Tire pressure monitoring system (TPMS)
The system covers the upper electronic module (UEM) (4/70) and the sensors in the wheels. The sensors in the wheels are activated when the vehicle exceeds 40 km/h (25 mph). The sensors then start to transmit data messages approximately once per minute, which are received by the remote control receiver in the Upper electronic module (UEM). These messages contain the sensor's ID number and air pressure in the tire where the sensor is mounted.
The frequency that the sensors transmit on is the same for all sensors. The control module can also receive signals from other vehicles with the same system installed. However, the ID number in each sensor is unique. The sensors that are mounted on the actual vehicle are determined by an elimination procedure in the Upper electronic module (UEM). When the ignition is switched on, the Upper electronic module (UEM) starts to listen for messages from the sensors. The control module registers the ID number found in the received messages that the sensors transmit, from the actual vehicle and other vehicles. The Upper electronic module (UEM) stores all ID numbers that are received in a list in its internal memory. For each ID number that is received, the number of times that that ID number is received is also saved. As the number of ID numbers received increases, the ID numbers received the most times are evaluated. The four ID numbers that have been received the most times receive the highest "calculation" and are considered to belong to the actual vehicle. In this way, any ID numbers that have been received from other vehicles can be differentiated. For example, ID numbers that are in another lane next to the actual vehicle. This evaluation takes approximately 5 minutes if the Upper electronic module (UEM) has no data.
If the evaluation has been carried out, the sensors that are assumed to belong to the actual vehicle are stored in the control module. The information remains between each driving cycle. In this case, it is sufficient for the control module to receive a message from each sensor with corresponding ID number to complete evaluation.
In Upper Electronic Module (UEM) there are tables programmed with which air pressure is recommended for this specific vehicle model. This information about air pressure in the tires included in the messages sent from the sensors is compared to the programmed values in Upper Electronic Module (UEM).
If the reported pressure from a sensor deviates by more than 22% from the recommended value, a warning message will be shown in the Driver information module (DIM).
There are two warning levels that generate different warning messages, one warning for low pressure and one warning for no pressure. A message will also be shown is a sensor should stop transmitting or should receive too low battery voltage.
To reset a warning it is easiest to stop the vehicle and fill air in the tire where the air pressure is low. In order for the warning to reset air has to be filled so that the air pressure reaches a level that corresponds to at least 95% of the recommended air pressure, and then drive the vehicle faster than 40 km/h (25 mph) for more than 10 minutes, accumulated time.
If the customer has come to the workshop, the warning can also be reset by filling air in the tire where the air pressure is low (up to min. 95% of the recommended air pressure) and then the sensor is activated with the special tool for activating the tire pressure sensor.
When air is filled and the pressure changes, the sensor immediately sends a signal to Upper Electronic Module (UEM). If the ignition is on, the warning is reset immediately.
Note! Only applies to USA/CDN. A warning lamp also lights in the Driver information module (DIM) at the same time as the warning message.
Compass
The compass detects the magnetic pull of the North and South Poles. Using this, the compass calculates the direction in which the front of the vehicle is pointing.
The display in the top right-hand corner of the rear view mirror shows the compass direction. Eight different directions can be displayed, using the abbreviations N, NE, E, SE, S, SW, W and NW.
- N: North
- NE: North East
- E: East
- SE: South East
- S: South
- SW: South West
- W: West
- NW: North West