Design [4 of 4]
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 to the horns is via a relay in the relay box in the engine compartment.
There are diagnostics for the relay for the horn.
Rear demist
There are heating loops in the glass for demisting and to prevent ice from forming. The loops heat up when they are supplied with power. The power supply is via a relay in the central electronic module (CEM).
Rear demist is controlled using a switch on the right-hand side of the climate control module (CCM).
Press the button again to switch off the function. Demisting is switched off automatically after the maximum time of 12 minutes.
On vehicles with certain diesel engines the rear demist can start without manual activation. This means that the engine sometimes needs to reach a much greater working temperature to burn soot particles that are trapped in the particle filter.
By starting the rear demist, together with other actions, the vehicle's alternator is loaded and the engine coolant temperature rises.
Read more detailed information about this function in Design and Function, Engine control module (ECM).
There are diagnostics for the relay and switch.
Switch clutch pedal (4-cylinder)
The clutch pedal switch is positioned together with the clutch pedal. In resting position the switch is open. It closes when the clutch pedal is pressed down by more than 90% of its entire stroke length. When the switch is activated, a signal is transmitted to the central electronic module (CEM).
For further information about the immobilizer, see Design and Function, Immobilizer.
Clutch pedal sensor (5-cylinder)
Cars with 5-cylinder gasoline engines have a position sensor for the clutch pedal. The sensor is affected when the clutch pedal is pressed. The sensor then sends a signal (voltage level) which is proportional to the degree to which the clutch pedal has been pressed.
The position sensor is directly connected to the central electronic module (CEM). The control module receives and processes the signal. The information is used in difference ways depending on the equipment level of the car.
The signal is used as part of the conditions for the immobilizer.
For further information about the immobilizer, see Design and Function, Immobilizer.
Power windows
All side windows are operated by motors in the doors. The switches for operating the windows are in each door panel. All windows can be operated from the control panel in the driver's door.
For further information, see Design and Function, Door control modules.
For greater comfort, all windows including the sun roof can be opened. This is done by holding in the unlock button on the remote control for 1.5 seconds. In the same way, all windows including the sun roof can be closed at the same time. This is done by holding in the lock button on the remote control for 1.5 seconds.
This function can also be activated from inside the passenger compartment. If the lock or unlock button is held in on either of the front door panels the same function will be obtained.
Fuel pump
The fuel pump (FP) is located on the inside of the fuel tank on the right-hand side. The pump is checked by the fuel pump control module. The central electronic module (CEM) controls a relay which powers the fuel pump control unit. The relay 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) to control the fuel pump (FP). There is also a directly connected cable between the engine control module (ECM) and the fuel pump control module. This is used to transmit a pulsed signal to operate the fuel pump (FP). For further information, see Design and Function, engine control module (ECM).
The central electronic module (CEM) also communicates with the supplemental restraint system (SRS) module via the controller area network (CAN). In the event of a collision, the supplemental restraint system module (SRS) transmits data and the central electronic module (CEM) shuts off the power supply to the fuel pump (FP).
There are diagnostics for the input signal from the engine control module (ECM) and the relay for the power supply to the fuel pump control module.
Fuel level (Gasoline/Diesel)
The fuel level in the tank is measured by a sensor. The sensor is on the pump side of the fuel tank. The sensor is directly connected to the central electronic module (CEM) on the same side as the DC/AC converter (only applies to B4184S8).
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 signal from the sensor is 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 fuel level sensor is faulty, the fuel gauge will show 0.
There are diagnostics for the fuel level sensor. In the event of a fault on the DC/AC converter (only applies to B4184S8) any fuel level measurement functions are affected.
The DC/AC converter fuel tank (only B4184S8)
The DC/AC converter functions as a corrosion preventative by producing alternating current on the inside of the fuel tank. The converter is directly connected to the Central electronic module (CEM) on the same terminal as the fuel level gauge. The converter is located on the left-hand side under the rear of the seat cushion.
There are diagnostics for the DC/AC converter. In the event of a fault with the fuel level gauge, the converter function will be affected.
Electrical additional heater (certain markets)
Vehicles with diesel engines have an electrical additional heater (PTC element) on certain markets.
This comprises a heater element with ceramic resistors located in the heater housing. The air that flows into the passenger compartment is heated directly.
For further information, see Design and Function, climate control module (CCM).
Battery temperature sensor (replaced by software starting from structure week 200605)
The battery temperature sensor checks the temperature of the battery. 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 sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal) and is grounded in the control module.
The resistance of the sensor changes with the temperature of the battery. This alters the signal to the central electronic module (CEM). At:
- +20 °C the resistance is approximately 3.5 kohms
- 0 °C the resistance is approximately 9.4 kohms
- -20 °C the resistance is approximately 28.6 kohms.
The lower the temperature the higher the resistance (high voltage). A high temperature results in low resistance (low voltage).
The battery temperature sensor is in the bottom of the battery box. The sensor is directly connected to the central electronic module (CEM).
The central electronic module (CEM) has diagnostics for the battery temperature sensor. The temperature can be read off using VIDA.
From structure week 200605, the battery temperature sensor has been replaced by software. Battery temperature is then calculated from four input signals: outside temperature, engine temperature, vehicle speed and power supply status. The function is diagnosed by the central electronic module (CEM). Temperature can be read off using VIDA.
If the central electronic module (CEM) detects a fault in the sensor or the calculation function, a substitute value of +55 °C is used. This generates a fixed generator output voltage of 13.5 V.
See also Design and Function, Regenerating brake energy (2010-).
Tire pressure monitoring system (TPMS)
The purpose of the tire pressure monitoring system, TPMS, is to enable the driver to have optimum tire pressure by giving a warning when the pressure in any of the tires becomes too low. Correct tire pressure is important for:
- achieving good fuel economy
- achieving optimum comfort and good driving characteristics
- preventing flat tires due to too low tire pressure.
The function is integrated in the central electronic module (CEM). Sensors are installed together with the air valve on each wheel to measure the air pressure in the tires.
Note! The system must be regarded as a driver aid to maintain the correct tire pressure. The system must NOT be regarded as a warning system that indicates that there is a serious problem with the vehicle. No tire is completely sealed - there is always slight leakage as the tire can never be completely sealed to the rim. When inflating the tire with air, you must, as much as possible, ensure that the tires are at same temperature as the outside temperature. Furthermore, "Comfort pressure" should not be applied as this gives a tire pressure that is too close to the parameter for the monitoring system, which means that even small changes in temperature or load can cause the pressure in the tires to be too low for the system to consider acceptable. When inflating with air, the tires must be filled to the pressure stated on the decal located on the car body. The pressure is calculated with regard to fuel economy, comfort and safety. Therefore, these pressures MUST be followed. If the decal is missing or damaged, a new one must be ordered and applied. This is especially important on vehicles with TPMS.
For more information, see Design and Function, System for Tire pressure monitoring (TPMS).
Tire pressure sensor
The tire pressure sensors are installed together with the air valve on the rim. The sensor consists of a pressure sensor, a communication circuit, an acceleration sensor and a battery.
Note! Special procedures are required for removing the tire from the rim depending on vehicle model and tire type. This is to prevent damaging the sensor. See the specific mechanical information instruction under Repairing/Removal, replacement and installation.
For more information, see Design and Function, System for Tire pressure monitoring (TPMS).