Design [1 of 4]

Design

Ignition switch




The ignition switch powers certain functions in the engine control module (ECM) via fuses in the front integrated relay/fuse box and central electronic module (CEM). The ignition switch also supplies the engine control module (ECM) with signals such as:
- "wake up" signal
- start signal.

"wake up" signal
The ignition switch transmits a high signal (Ubat) to the engine control module (ECM) via the central electronic module (CEM) indicating that the ignition switch is in position I or II. The system prepares for start-up (for example by temporarily activating the fuel pump relay).

Start signal
The ignition switch transmits a high signal (Ubat) to the engine control module (ECM) when the ignition switch is in position III.
The engine control module (ECM) activates the starter motor relay. The relay in turn activates the starter motor. See also: Function, B5244S4 Function
The fuse in the front integrated relay/fuse box supplies current to the ignition switch.
The central electronic module (CEM) has diagnostics for the ignition switch.

Transmission control module (TCM)




The engine control module (ECM) uses a directly connected signal from the transmission control module (TCM) in the start function (activating the starter motor). See also: Function, B5244S4 Function

Immobilizer
See Design and Function, Immobilizer.

Alternator control module (ACM)
See Design and Function, Generator (GEN).

Premair sensor (certain markets only) (2006-)




The function of the Premair sensor is to meet legal requirements for low emission variants. The sensor is located on the radiator.
The sensor measures the temperature of the radiator and transmits the value, together with a check of its own condition, to the Engine control module (ECM). During the engine's warm-up phase the Engine control module (ECM) carries out a number of checks of the received information in order to determine the status of the sensor and the radiator.
The sensor communicates with the Engine control module (ECM) via LIN (Local Interconnect Network)communication, a standardized serial communication method. Transmitted information is encrypted.
The Premair sensor is diagnosed by the Engine control module (ECM). The sensor is secured to the radiator and cannot be replaced separately.

Air conditioning (A/C) pressure switch




The air conditioning (A/C) pressure sensor detects the pressure in the low pressure side of the air conditioning (A/C) system. See also: Function, B5244S4 Function
The air conditioning (A/C) pressure sensor has a pressure sensing switch which is supplied powered by the fuse and grounded (signal) in the engine control module (ECM). The air conditioning (A/C) pressure sensor is affected by the pressure in the low-pressure pipe of the air conditioning (A/C) system (thick pipe).
The engine control module (ECM) cannot diagnose the air conditioning (A/C) pressure sensor.

Oil pressure switch




The function of the oil pressure switch is to warn the driver about low oil pressure via the driver information module (DIM).
The oil pressure switch has a pressure sensing switch which is powered (signal) by the engine control module (ECM) and grounded in the cylinder block. The oil pressure sensor is affected by the oil pressure of the engine.
When the oil pressure exceeds a certain value, the switch in the oil pressure sensor will open. A high signal is then sent to the engine control module (ECM).
If the oil pressure is below a certain value, the switch in the oil pressure sensor will close and a high signal will be sent to the engine control module (ECM). The engine control module (ECM) then transmits a CAN signal to the driver information module (DIM) to light the indicator lamp for low oil pressure.
The oil pressure sensor is on the cylinder block.
The engine control module (ECM) cannot diagnose the oil pressure sensor.

Fuel pump control module




The fuel pump control module powers the fuel pump and regulates the output of the pump. The fuel pressure changes with the output of the pump.
The fuel pump control module is supplied with battery voltage by the fuel pump (FP) relay and is grounded in the car body. The fuel pump (FP) relay is controlled by the central electronic module (CEM) when requested by the engine control module (ECM).
The engine cannot be started if the power supply to the fuel pump control module is faulty because the fuel pump will not then be powered.
The fuel pump control module is controlled by the engine control module (ECM) via serial communication. The fuel pump control module then controls the fuel pump by transmitting pulse width modulated (PWM) voltage on the ground lead for the fuel pump. This means that the voltage drop across the pump changes, and with it the output of the fuel pump. See also: Function, B5244S4 Function
There are no diagnostics for the fuel pump control module. The engine control module (ECM) has diagnostics for fuel pressure regulation and the associated components. See also: Fuel pressure regulation, diagnostics Fuel Pressure Regulation, Diagnostics
The pulse-width modulated (PWM) signal from the engine control module (ECM) to the fuel pump control module can be read using VIDA.
The fuel pump control module is on the outside on the right-hand side of the fuel tank.

Fuel pump




The function of the fuel pump is to ensure that the pressure is correct at the delivery lines for the injectors when requested by the fuel pump control module.

The fuel pump consists of:
1. An electrical pump with an integrated safety valve
2. A pressure equalization valve. This valve equalizes rapid pressure peaks which occur, for example, when the injectors close during engine braking. It also contains a non-return valve which ensures that the pressure in the system does not drop when the engine is switched off
3. Fuel level sensor
4. Fuel filter, cannot be replaced separately
5. Relief valve, releases fuel into the pump housing
6. Ejector pump, continuously fills the pump housing with fuel. The fuel always flows from the fuel pump through the ejector and back to the pump housing.
The fuel pump is supplied with battery voltage by the fuel pump control module and is grounded in the car body via the fuel pump control module.
The engine control module (ECM) has diagnostics for the fuel pump function to ensure that the pressure is correct. See also: Fuel pressure regulation, diagnostics Fuel Pressure Regulation, Diagnostics
The fuel pump can be activated and its status read off using VIDA.
The pressure in the fuel rail can be measured by connecting a manometer to a nipple. This nipple is on the right-hand end of the fuel rail.

Stop lamp switch




The task of the stop lamp switch is to provide the engine control module (ECM) with information about the position of the brake pedal.
A signal is transmitted to the engine control module (ECM) when the brake pedal is pressed. The engine control module (ECM) disengages the cruise control (if activated). The brake pedal sensor also disengages cruise control. For further information, see Design and Function, Brake control module (BCM), design.
The stop lamp switch is supplied with power from the ignition switch (terminal 30). When the brake pedal is depressed the switch closes and a high signal (12 V) is transmitted to the engine control module (ECM).
The engine control module (ECM) can diagnose the brake light switch. The status of the switch can be read using VIDA.
The stop lamp switch is on the pedal box by the brake pedal.

A/C pressure sensor




The air conditioning (A/C) pressure sensor detects the pressure in the high-pressure side of the air conditioning (A/C) system. See also: Function, B5244S4 Function
The sensor is linear. It is grounded in the control module and supplied with a 5 Volt current from the control module. A linear signal (between 0-5 V depending on the pressure in the air conditioning (A/C)) is transmitted to the control module. Low pressure produces low voltage, high pressure produces high voltage. The air conditioning (A/C) pressure sensor is affected by the pressure in the high-pressure pipe of the air conditioning (A/C) system (narrow pipe).
The engine control module (ECM) can diagnose the air conditioning (A/C) pressure sensor. The sensor value can be read off using VIDA.

Heated oxygen sensors (HO2S)

Front heated oxygen sensor (HO2S)





Caution! The air lines for the heated oxygen sensors must not be trapped or damaged in any way. The connectors for the heated oxygen sensors must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors.

The front heated oxygen sensor (HO2S) is used to provide the engine control module (ECM) with information about the remaining oxygen content of the exhaust gases in front of the three-way catalytic converter (TWC). This is so that the Engine Control Module (ECM) can continually check the combustion so that lambda=1. lambda=1 is the ideal fuel-air ratio, with 14.7 kg air per 1 kg fuel.
The heated oxygen sensor (HO2S) uses current control and its signal characteristic is linear. With a linear signal characteristic, the amplitude of the signal curve is low when the oxygen content in the exhaust gases changes. The probe consists of a preheating element (see "Pre-heating heated oxygen sensors (HO2S)") and the actual lambda sensor. The lambda sensor is an oxygen sensitive ceramic body consisting of zirconium oxide. The control module supplies power to the ceramic body, which reacts to the oxygen content of the exhaust gases. This in turn affects the signal to the engine control module (ECM). In order to determine the oxygen content in the exhaust pipe, the heated oxygen sensor (HO2S) needs reference air from the surrounding air. This reference air reaches the heated oxygen sensor (HO2S) via the air lines.

Caution! The air lines for the heated oxygen sensors must not be trapped or damaged in any way. The connectors for the heated oxygen sensors must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors.

The engine control module (ECM) can diagnose the heated oxygen sensor (HO2S). For more information, see: Heated oxygen sensor (HO2S) diagnostic Description and Operation
VIDA can be used to read off the calculated lambda value from the heated oxygen sensor.

Center heated oxygen sensor (HO2S) (certain markets only)





Caution! The air lines for the heated oxygen sensors must not be trapped or damaged in any way. The connectors for the heated oxygen sensors must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors.

Some vehicles have 3 heated oxygen sensors (HO2S), front, center and rear.
The center heated oxygen sensor (HO2S) is the same type as the rear. However it has a different part number to differentiate it from the rear heated oxygen sensor (HO2S).
The center heated oxygen sensor (HO2S) is used
- to provide the engine control module (ECM) with information about the remaining quantity of oxygen in the exhaust gases. This information is provided more quickly than in vehicles with only a front and rear heated oxygen sensor (HO2S)
- to allow quicker start of exhaust purification
- for regulation when the engine is under low loads.
The center heated oxygen sensor (as with the rear heated oxygen sensor (HO2S)) uses voltage control. The signal characteristic is binary. With a binary signal characteristic, the amplitude of the signal curve changes considerably when changing the oxygen content in the exhaust gases.

Caution! The air lines for the heated oxygen sensors must not be trapped or damaged in any way. The connectors for the heated oxygen sensors must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors.

The engine control module (ECM) can diagnose the center heated oxygen sensor (HO2S). The signal can be read using VIDA.
For more information, see Heated oxygen sensor (HO2S) diagnostic Description and Operation