Throttle Position (TP) Sensor
See Electronic throttle unit .
Scheme 113
The function of the accelerator pedal (AP) position sensor is to provide the engine control module (ECM) with information about the position of the accelerator pedal. This data is used by the control module to deploy the shutter in the throttle unit to the correct angle.
The sensor consists of a plastic housing with two potentiometers, an Analog/Digital converter and circuits. The potentiometers are connected to a shaft which is affected by the position of the accelerator pedal (AP). The resistance in the potentiometers changes with the position of the accelerator pedal (AP).
The accelerator pedal (AP) position sensor transmits an analogue and a digital signal (pulse width modulated (PWM) signal) to the control module. 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 control module to regulate the throttle shutter angle.
The sensor is supplied with 12 V by the system relay via a fuse and is grounded to the body.
The digital signal is also used in conjunction with the analog signal for accelerator pedal position sensor diagnostics. The accelerator pedal (AP) position sensor signals can be read off using appropriate diagnostics tool. 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.
Scheme 114
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 chassis. 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 following applies from model year 2005
The signal of the engine coolant level sensor can be read using appropriate diagnostics tool.
The engine control module (ECM) cannot diagnose the engine coolant level sensor.
Scheme 115
On naturally aspirated engines, the intake air temperature sensor is integrated in the mass air flow (MAF) sensor. On model year 2002 turbocharged engines, the temperature sensor is a stand-alone component. On turbocharged engines from model year 2003, the temperature sensor is integrated in the intake air pressure 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 (turbocharger (TC) 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 V. The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).
The temperature sensor is between the air cleaner (ACL) housing and the intake manifold (does not apply to turbocharged engines 2003-). The temperature sensor on turbocharged engines 2003- is integrated in the intake air pressure sensor.
The engine control module (ECM) can diagnose the temperature sensor. The sensor signal can be read using appropriate diagnostics tool.
Scheme 116
The fuel pressure sensor is combined and consisted of both the fuel pressure sensor and the fuel temperature sensor. The sensor detects the fuel pressure (the absolute pressure) and the temperature of the fuel in the fuel rail.
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. Low pressure results in low voltage, high pressure in 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. Also see Fuel pressure regulation (only vehicles with demand controlled fuel pumps) .
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.
The engine control module (ECM) can diagnose the fuel pressure sensor. Its signals (pressure and temperature) can be read using appropriate diagnostics tool.
Note. The absolute pressure is displayed when using appropriate diagnostics tool parameter readout 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.
The fuel pressure sensor is on the left-hand end of the fuel rail.
Scheme 117
The oil level sensor provides the engine control module (ECM) with information about the quality and temperature of the engine oil and the oil level in the oil trough. Which of these functions is used by the sensor varies between different car models.
All three functions are combined in one unit with a sensor section and an electronics section. There are no moving parts in the sensor.
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 PWM signal for the engine control module (ECM). Also see Oil level monitoring (2004-, certain markets and models only) .
The engine control module (ECM) can diagnose the functions of the oil level sensor. Also see Oil Level Sensor, Diagnostics (2004-, Certain Markets And Models Only) .
The pulse-width modulated (PWM) signal from the oil level sensor can be read using parameter readout.
Scheme 118
The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing 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 engine control module (ECM) can diagnose the main relay.
The main relay is in the relay/fusebox in the engine compartment.
Scheme 119
The air conditioning (A/C) relay supplies the A/C compressor with voltage. The relay is controlled by the engine control module (ECM) based on information from different signals
- the climate control module (CCM) (via the control area network (CAN))
- the engine coolant temperature
- the position of the accelerator pedal (AP)
- the pressure in the system.
The Engine Control Module (ECM) can temporarily disengage the A/C compressor during wide open throttle (WOT) acceleration.
The relay is mechanical. It has a closing / breaking function and is supplied with power from the system relay.
In the rest position the circuit in the relay is open.
The system relay supplies the coil and the relay with power. The relay activates when the coil is grounded in the engine control module (ECM), the circuit closes and the A/C compressor is supplied with power via the relay voltage output.
The relay coil is grounded (signal) when the engine control module (ECM) receives a signal via the Controller area network (CAN) from the climate control module (CCM) to activate the relay and start the compressor.