Part 2

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.

Stop lamp switch




The purpose of the stop lamp switch is to provide the engine control module (ECM) with information indicating whether the brake pedal is depressed or not.
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 system, 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 stop lamp switch can be diagnosed by the engine control module (ECM) and its status (depressed or not) can be read off.
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.
The sensor is linear. It is grounded in the control module and supplied with 5 V from the control module. A linear signal (which depends on the pressure in the air conditioning (A/C) system) is transmitted to the engine control module (ECM). Low pressure produces low voltage, high pressure produces high voltage.
The air conditioning (A/C) pressure sensor can be diagnosed by the engine control module (ECM) and the sensor value can be read off.
The air conditioning (A/C) pressure sensor is directly mounted on the air conditioning receiver drier.

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).

Accelerator pedal (AP) position sensor




The function of the accelerator pedal (AP) position sensor is to provide the engine control module (ECM) and central electronic module (CEM) with information about the position of the accelerator pedal. This data is used by the engine control module (ECM) to deploy the shutter in the throttle unit to the correct angle.
The accelerator pedal (AP) position sensor consists of a plastic housing with two potentiometers, and an Analog/Digital converter. The potentiometers are connected to a common shaft which is affected by the position of the accelerator pedal (AP).
The accelerator pedal (AP) position sensor transmits an analog and a pulse width modulated (PWM signal to the engine control module (ECM). These signals indicate the position of the accelerator pedal (AP). The digital signal is generated by the sensors Analog/Digital converter.
The analog and digital signals are used at the same time by the engine control module (ECM) to regulate the throttle shutter angle.
The power supply to the two potentiometers is different. The analog potentiometer is supplied with 5 V via the engine control module (ECM). The digital potentiometer is supplied with 12 V via the system relay and is grounded in the car body.
The digital signal is also used in conjunction with the analog signal for accelerator pedal (AP) position sensor diagnostics.
Accelerator pedal (AP) position sensor signals can be read off.
A diagnostic trouble code (DTC) is stored if the engine control module (ECM) detects a difference between the analog and digital signals. The engine control module (ECM) then uses a minimal value to ensure the function (limp home).
The accelerator pedal (AP) position sensor is located on the accelerator pedal bracket.

Outside temperature sensor




The outside temperature sensor detects the temperature in the surrounding air. The signal is used by the engine control module (ECM) as a substitute value in the event of a fault in certain components or functions and to control certain diagnostic functions.
The sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal). The resistance in the sensor changes with the outside temperature. This alters the signal to the engine control module (ECM). The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).
The outside temperature sensor is positioned in the left door mirror.
The outside temperature sensor can be diagnosed by the engine control module (ECM) and the sensor value can be read off.

Engine coolant level sensor




The function of the engine coolant level sensor is to alert the driver if the engine coolant level in the expansion tank is too low.
The sensor is a magnetic reed switch, which is enclosed in a pipe on the bottom of the expansion tank. Around the pipe, on the inside of the expansion tank is a float. This float contains a magnet. When the engine coolant level is above minimum, the float is too high in the tank to affect the switch. However if the engine coolant level falls below the minimum level, the magnetic field acts on the switch.
The sensor is supplied with voltage (signal) from the engine control module (ECM) and grounded in the body. When the engine coolant level in the expansion tank is over a certain level the circuit closes, which produces a low signal. When the engine coolant level is below a certain level the circuit is opened by the engine coolant level sensor, which produces a high signal. When the engine control module (ECM) detects a high signal the information about low engine coolant level is transmitted via the Controller area network (CAN) to the driver information module (DIM), which warns the driver.

Note! There are no functions controlled by the engine which are directly connected to the low coolant level warning lamp. The Engine Control Module (ECM) only transfers the signal which is used by the Driver Information Module (DIM).

The engine control module (ECM) cannot diagnose the engine coolant level 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 switch is affected by the oil pressure of the engine.
When the oil pressure exceeds a certain value, the switch in the oil pressure switch 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 switch will close and a low 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 switch.

Manifold absolute pressure (MAP) sensor, intake




The manifold absolute pressure (MAP) sensor detects quick pressure changes in the intake manifold after the throttle. The signal from the sensor is used by the engine control module (ECM) to supplement the mass air flow (MAF) sensor when calculating injection period.
The manifold absolute pressure (MAP) sensor intake is located on the upper rear edge of the engine (passenger compartment side).
The semi-conductor sensor is grounded in the control module and is supplied with power from the control module.
The resistance in the intake manifold moves the silicone membrane in the sensor, giving a signal of 0.5 - 4.5 V to the control module. Low pressure results in low voltage, high pressure gives high voltage.
The pressure sensor can be diagnosed by the engine control module (ECM) and the sensor signal can be read off.

Fuel pressure sensor / fuel temperature sensor





Overview
The fuel pressure and fuel temperature sensors are combined.
The sensor detects the fuel pressure (absolute pressure) and the temperature of the fuel in the fuel rail.
The fuel pressure sensor is on the right-hand end of the fuel rail.
The fuel pressure-/fuel temperature sensor can be diagnosed by the engine control module (ECM) and its signals (pressure and temperature) can be read off.

Fuel pressure sensor
The pressure sensor is a Piezo resistive type resistor, the resistance of which changes with the pressure. Depending on the pressure in the fuel rail, an analog signal of 0 - 5 V is transmitted to the engine control module (ECM). Low pressure results in low voltage, high pressure gives high voltage.
The engine control module (ECM) then uses this signal to adjust the pressure in the fuel rail using the fuel pump control module. See also: Function, B8444S Function
The pressure sensor is supplied with 5 V and grounded in the engine control module (ECM). The pressure sensor transmits a signal indicating the fuel pressure to the engine control module (ECM) on a separate cable.

Note! The absolute pressure is displayed when using parameter read outs to read off the fuel pressure. If there is no pressure at the fuel rail, the atmospheric pressure will be displayed.

Hint: The relative pressure (absolute pressure minus atmospheric pressure) is displayed when reading off the fuel pressure via a manometer connected to the fuel rail.

Fuel temperature sensor
The temperature sensor is an NTC sensor. The sensor is supplied with voltage (signal) from and grounded in the engine control module (ECM).
The resistance in the sensor changes according to the temperature of the fuel. This provides the engine control module (ECM) with a signal of between 0 - 5 V. Low temperature results in high voltage (high resistance). High temperature results in low voltage (low resistance).
The engine control module (ECM) uses the signal to calculate the volume of the fuel.

Oil level sensor




The function of the oil level sensor is to provide the engine control module (ECM) with information regarding the level of engine oil in the oil sump.
The sensor consists of:
- a terminal with three pins
- integrated electronics
- 2 capacitive gauge elements
- a PTC resistor.
The oil level sensor is supplied with 5 V by the engine control module (ECM). The oil level sensor generates a pulse width modulated (PWM) signal for the engine control module (ECM).
The oil level sensor can be diagnosed by the engine control module (ECM).
The pulse-width modulated (PWM) signal from the oil level sensor can be read using parameter readout.

Main relay (system relay)




The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing and opening function. In the rest position the circuit in the relay is open.
The main relay terminals (#30 and #86) are supplied with voltage by the battery. When the ignition key has been turned and the engine control module (ECM) is powered, the terminal (#85) on the main relay is grounded by the engine control module (ECM).
When the terminal (#85) is grounded, the relay is activated and a number of components are powered via the relay terminal (#87).
The main relay is in the integrated relay/fuse box in the engine compartment and is diagnosed by the engine control module (ECM).

Injectors




The function of the injectors is to spray fuel into the cylinders in the correct spray patterns. This happens sequentially.
The injectors are located under the intake manifold.
The engine control module (ECM) controls the injectors by grounding the valves in pulses.
The injectors can be diagnosed by the engine control module (ECM) and can be activated.