Part 1

Design

Start control module (SCU)

The start control module (SCU) with start button and card holder is the unit which is used by the driver to start the vehicle. See also Design and Function, Immobilizer.
Start control module (SCU) activate the voltage supply to certain functions in the engine control module (ECM) via fuses in the front relay/fuse box and central electronic module (CEM). Start control module (SCU) supplies the engine control module (ECM) with a start signal.
Start control module (SCU) transmits a high signal (Ubat) to engine control module (ECM) when start control module (SCU) is in position III.
The engine control module (ECM) will activate the starter motor relay. In turn the relay activates the starter motor.
Start control module (SCU) is supplied with voltage from the fuse in the front relay / fuse box.
The central electronic module (CEM) can diagnose the start control module (SCU).

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).

Immobilizer
See Design and Function, Immobilizer.

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

Fuel pump control module

The fuel pump control module is called the PEM (Pump Electronic Module). The function of the PEM is to supply the fuel pump with voltage and to control the power output of the fuel pump. When the power output of the pump is changed the fuel pressure is also changed.
The pump electronic module (PEM) 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 pump electronic module (PEM) is controlled by the engine control module (ECM) via serial communication. The pump electronic module (PEM) 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.
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 pump electronic module (PEM) can be read off using the diagnostic tool.
The fuel pump control module is on the outside on the right-hand side of the fuel tank.

Fuel pump (USA/CAN)

The fuel pump function is to ensure that the correct pressure and flow is retained at the fuel rail at the request of the engine control module (ECM).
The fuel pump are supplied electrically via the pump electronic module (PEM) with variable effect to be able to supply variable fuel pressure/flow and grounded in the bodywork via the pump electronic module (PEM).
The engine control module (ECM) can diagnose the fuel pump function for the correct pressure and electronic open circuit. The engine control module (ECM) can diagnose the pump electronic module(PEM). See also: Fuel pressure regulation, diagnostics Fuel Pressure Regulation, Diagnostics
The fuel pump can be activated and its status read off using the diagnostic tool.
The pressure in the fuel rail can be measured by connecting a manometer to a service nipple. This nipple is on the right-hand end of the fuel rail.

Fuel pump other

The task of the brake light 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).
The stop lamp switch is supplied with power from the start control module (SCU) (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 the diagnostic tool.
The stop lamp switch is on the pedal box by the brake pedal.

Clutch pedal switch (manual transmissions only)

The purpose of the clutch pedal switch is to give the engine control module (ECM) information about the position of the clutch pedal. The clutch pedal switch directly connected to the engine control module (ECM).
Because the communication on the HS-CAN can temporarily fail during the starting sequence two information sources are used for the clutch pedal position. This is to prevent interference during starts. The engine control module (ECM) also receives information about the clutch pedal position via the central electronic module (CEM). See also Design and Function, Central electronic module (CEM).
The clutch pedal switch is open in its original position (clutch pedal not depressed) and is supplied with voltage from the start control module (SCU) (terminal 30). When the clutch pedal is depressed more than 75% 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 clutch pedal switch and the status (position) can be read off using the diagnostic tool.
The clutch pedal switch is located on the pedal box by the clutch pedal.

Air conditioning (A/C) compressor

The air conditioning (A/C) pressure sensor detects the pressure in the high-pressure side of the air conditioning (A/C) system.
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 the diagnostic tool.

Heated oxygen sensors (HO2S)
There are two heated oxygen sensors (HO2S), front and rear.

Front heated oxygen sensor (HO2S)

Caution! The 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 rear heated oxygen sensor (HO2S) is used to provide the Engine Control Module (ECM) with information about the remaining oxygen content of the exhaust gases behind the three-way catalytic converter (TWC). This information is used by the Engine Control Module (ECM) to check the function of the three-way catalytic converter (TWC). This check is carried out when the conditions for the catalytic converter diagnostics have been met. The rear heated oxygen sensor (HO2S) has no direct effect on regulation of the fuel/air mixture. However the Engine Control Module (ECM) uses the signal to optimize the signal from the front heated oxygen sensor (HO2S). For more information, see: Three-way catalytic converter (TWC) diagnostics Three-Way Catalytic Converter (TWC) Diagnostics
The 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. Otherwise its components and function are the same as the front heated oxygen sensor (HO2S).
The engine control module (ECM) can diagnose the rear heated oxygen sensor. The signal can be read using the diagnostic tool.

Preheating of the heated oxygen sensors (HO2S)
The heated oxygen sensor (HO2S) only functions above a certain temperature, approximately 300 °C. The normal operating temperature is between 300-900 °C. The heated oxygen sensors (HO2S) are electrically pre-heated so that operating temperature is rapidly reached. This also ensures that the heated oxygen sensors (HO2S) maintain a normal operating temperature and to prevent condensation which could damage the heated oxygen sensor (HO2S).
The heater element in the probe consists of a positive temperature coefficient (PTC) resistor. The system relay supplies the heater element with voltage. The element is grounded in the engine control module (ECM). When the control module grounds the connection a current flows through the PTC resistor. When the heated oxygen sensor (HO2S) is cold, the resistance in the PTC resistor is low and a large current will flow through the circuit. The current from the Engine Control Module (ECM) is pulsed at first to prevent condensation damage to the heated oxygen sensor (HO2S). Depending on the temperature, allowances are made for factors such as the dew point. As the temperature in the PTC resistor rises, the resistance rises, the current falls and switches in stages to a constant current. The pre-heating time for the front heated oxygen sensor (HO2S) is short, approximately 20 seconds.
Probe preheating begins as soon as the engine is started. The heater element heats the heated oxygen sensors (HO2S) to approximately 350 °C. The probes maintain this as a minimum temperature.
The engine control module (ECM) can diagnose the heater element.

Engine coolant temperature (ECT) sensor

The engine coolant temperature (ECT) sensor checks the temperature of the engine coolant. The temperature of the engine coolant is required so that the engine control module (ECM) can regulate:
- the injection period
- the idle speed
- the engine cooling fan (FC)
- the ignition advance
- engagement and disengagement of the A/C compressor
- diagnostic functions.
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 in the sensor changes depending on the temperature of the coolant. Depending on the resistance in the sensor, a voltage (signal) is transmitted to the Engine Control Module (ECM). At 0 °C, the voltage is approximately 4.0 V. At 100 °C the voltage is approximately 0.5 V. Low temperature results in high voltage (high resistance), high temperature in low voltage (low resistance).
The engine coolant temperature (ECT) sensor is located beside the thermostat.
The engine control module (ECM) can diagnose the engine coolant temperature sensor. The sensor value can be read off using the diagnostic tool.

Outside temperature sensor

The outside temperature sensor function is to detect the vehicle's ambient temperature. It is necessary for the engine control module (ECM) to know the vehicle's ambient temperature so that the following can be controlled:
- the engine cooling fan (FC)
- The air conditioning (A/C) compressor's displacement.
The ambient temperature is also used as a substitute value in the event of certain faults or functions and to control certain diagnostic functions.
The temperature sensor is a resistor with negative temperature coefficient, so called NTC type. This is supplied with voltage from the control module.
The resistance in the sensor changes depending on the ambient temperature of the vehicle. This gives a signal between 0-5V to the engine control module (ECM). Low temperature results in high resistance (high voltage). High temperature in low resistance (low voltage). At -10 °C the resistance is approximately 10.7 Mohms, at 0 °C the resistance is approximately 6.3 Mohms and at 20 °C resistance is approximately 2.4 Mohms.
The outside temperature sensor is located in the left-hand door mirror.
The engine control module (ECM) can diagnose the outside temperature sensor. The sensor value can be read off using the diagnostic tool.

Engine cooling fan (FC) / engine cooling fan (FC) control module

Note! the engine cooling fan (FC) may run on for approximately 6 minutes after switching off the engine. The time for the engine cooling fan run on depends on the engine's temperature, the temperature in the engine compartment and pressure level of the air conditioning (A/C) system.

Warning! Because the engine cooling fan (FC) can run on after the engine has been switched off great care must be taken.

The engine cooling fan (FC) has two functions. One is to cool the engine compartment, the other is to cool the condenser when the air conditioning (A/C) compressor is working.
The engine control module (ECM) transmits a pulse width modulated (PWM) signal to the engine cooling fan (FC) control module. The control module then activates the fan at different speeds. The speed of the engine cooling fan (FC) is determined by the engine control module (ECM), depending on the coolant temperature (based on the signal from the engine coolant temperature (ECT) sensor) and the vehicle speed.
The temperature conditions for engagement of the different engine cooling fan (FC) stages may vary slightly, depending on the engine variant and the equipment level. The temperature conditions apply when:
- the A/C is off
- no faults are detected by the Engine Control Module (ECM).
The engine cooling fan (FC) and its control module are behind the radiator.
The engine control module (ECM) can diagnose the engine cooling fan. The fan can be activated using the diagnostic tool.

Mass air flow (MAF) sensor

The mass air flow (MAF) sensor gauges the air mass sucked into the engine, regardless of the air's density and temperature. It continuously transmits signals to the engine control module (ECM) about the mass of the intake air. This data is used by the engine control module (ECM) to calculate:
- the engine load
The information is also used to determine:
- injection period
- fuel pressure
- the ignition timing
- turbocharger (TC) boost pressure (turbocharged engines only)
- Camshaft control (CVVT)
The transmission control module (TCM) also uses this data for its gear shift calculations. This data is transmitted to the transmission control module (TCM) from the engine control module (ECM) via the high speed side of the Controller area network (CAN).
The mass air flow (MAF) sensor consists of a plastic housing with connector and electronics as well as a sensor chip. The sensor chip is of a thin design, where two heat sensitive sensors are positioned in line and on each side of a heat generating sensor, one upstream and one downstream. When the chip is subjected to a flow of air, there is a temperature difference between the sensors, which is converted to a resistance difference. This is detected electrically by a so-called Wheatstone bridge, and is converted to mass air flow.
The mass air flow (MAF) sensor is supplied with battery voltage by the system relay and is connected to a 5 volt reference voltage and grounded from the engine control module (ECM). The signal from the sensor is analogue and varies between approximately 1-5 V depending on air mass. Low air flow (low mass) results in low voltage, high air flow (high mass) gives high voltage. No air flow gives a reading of approximately 1 V.
The mass air flow (MAF) sensor is positioned between the air cleaner (ACL) housing and the intake manifold.
The engine control module (ECM) can diagnose the mass air flow (MAF) sensor. The signal can be read using the diagnostic tool.

Charge pressure sensor

Overview
The boost pressure sensor is a combined sensor and contains two sensors in the same component:
- manifold absolute pressure (MAP) sensor
- temperature sensor.
The boost pressure sensor is on the right-hand upper section of the charge air cooler (CAC).
Manifold absolute pressure (MAP) sensor
The manifold absolute pressure (MAP) sensor detects the pressure in the intake manifold downstream of the charge air cooler (CAC). The signal from the sensor is primarily used by the engine control module (ECM) to check that the correct boost pressure is reached. The boost pressure is governed by the turbocharger (TC) control valve.
The sensor, which is a piezo resistor, is grounded in the control module and supplied with 5 V from the control module.
The resistance in the sensor changes depending on the pressure in the intake manifold, giving a signal of 0.5-4.5 V. Low pressure results in low voltage, high pressure on high voltage.
The engine control module (ECM) can diagnose the air pressure sensor. The sensor signal can be read using the diagnostic tool.
Temperature sensor
The temperature sensor detects the temperature of the intake air after the charge air cooler (CAC). This data is used by the engine control module (ECM) to calculate the boost pressure control and to calculate the injection period. The control module also controls certain diagnostic functions using the signal from the temperature sensor.
The sensor, which is an NTC resistor, is grounded in the control module and supplied with power (signal) from the control module.
The resistance in the sensor changes according to the temperature of the intake air. This provides the control module with a signal of between 0.5-5 V. The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).
The engine control module (ECM) can diagnose the temperature sensor. The sensor signal can be read using the diagnostic tool.