Part 3

Design (Continued)

Fuel pressure sensor / fuel temperature sensor (only vehicles with demand controlled fuel pumps)




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 Function, B5244T5, B5254T2 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.
The engine control module (ECM) can diagnose the fuel pressure sensor. Its signals (pressure and temperature) can be read using VIDA.

Note! The absolute pressure is displayed when using VIDA 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.

Oil level sensor (2004-, certain markets and models only)




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 Function, B5244T5, B5254T2 Function.
The engine control module (ECM) can diagnose the functions of the oil level sensor. Also see Oil level sensor, diagnostics Testing and Inspection.
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 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.

Air conditioning (A/C) relay




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.

Fuel pump (FP) relay, (2002-2004)




For information about the fuel pump (FP) relay for model year 2005-, see Design and Function, central electronic module (CEM).
The following applies for model year 2002-2004
The fuel pump (FP) relay supplies the fuel pump with power. The relay also cuts the power to the pump when the ignition is switched off or if the engine stops. In cars with demand controlled fuel pumps, the above function applies to the fuel pump control module. The central electronic module (CEM) also cuts the power to the relay if the supplemental restraint module (SRS) transmits a message indicating that an airbag has deployed.
The central electronic module (CEM) activates and deactivates the relay when requested by the engine control module (ECM) (via the Controller area network (CAN)).
See Design and Function, central electronic module (CEM).
When the ignition is switched on, the engine control module (ECM) sends a signal to the central electronic module (CEM) via the controller area network (CAN) to run the fuel pump (FP) for one seconds. This is so that the pressure increases in the fuel system, shortening the start time.
When the flywheel in the engine rotates (generating a signal from the engine speed (rpm) sensor), the engine control module (ECM) will transmit a request to the central electronic module (ECM) via the controller area network (CAN) to start the fuel pump. In the event of the engine stopping, the Engine Control Module (ECM) cancels the "activated fuel pump" signal. The central electronic module (CEM) then switches off the fuel pump.
There is a directly connected cable between the engine control module (ECM) and the central electronic module (CEM). In the event of a fault in the controller area network (CAN), this cable is used for the "activated fuel pump" signal.

Injectors




The function of the injectors is to spray fuel into the cylinders in the correct spray patterns. This happens sequentially.
The injectors are in the intake manifold.
It is essential that the injectors are correctly installed with no air leakage around them. Fuel leakage from the top of an injector when it is not activated may lead to starting and driving problems.
The engine control module (ECM) controls the injectors using a pulse width modulation (PWM) signal.
The injectors for each cylinder have different terminals in the engine control module (ECM), depending on whether the engine has 5 or 6 cylinders.
The engine control module (ECM) can diagnose the injectors. The injectors can be activated using VIDA.

evaporative emission system (EVAP) valve




The evaporative emission system (EVAP) valve is used to open/close the connection between the EVAP canister and the intake manifold. The valve controls the flow of hydro-carbons (fuel vapor) from the EVAP canister to the engine intake manifold using the vacuum in the intake manifold. This ensures that hydro-carbons stored in the EVAP canister are used in the engine combustion process.
The valve is an electro-magnetic valve which is powered from the system relay. When the valve needs to be opened, it is grounded internally in the engine control module (ECM). The evaporative emission system (EVAP) valve is closed when in the standby position (open-circuit).
When the control module requests that the EVAP canister should be emptied (the hydrocarbons stored in the canister should be released into the engine), the control module deploys the evaporative emission system (EVAP) valve by grounding it. The valve is grounded using a pulse width modulation (PWM) signal, allowing the control module to govern the extent to which the valve opens and adapting the emptying of the canister according to how full it is, engine speed (rpm) and load etc.
The engine control module (ECM) can diagnose the evaporative emission system (EVAP) valve. The valve can be activated using VIDA.
The evaporative emission system (EVAP) valve is close to the intake manifold.

Camshaft reset valve (Continuous variable valve timing (CVVT))




The camshaft reset valve controls the oil flow to the CVVT unit (camshaft pulley).
The valve consists of an electro-magnetic valve with a spring-loaded piston. There are slits in the piston which channel the engine lubricating oil to the CVVT unit by moving the piston in the reset valve. The continuous variable valve timing (CVVT) unit turns the camshaft (the cam timing changes). The direction in which the camshaft turns depends on the chamber in the CVVT unit which is supplied with oil (pressure). Also see Function, B5244T5, B5254T2 Function.
The system relay supplies the reset valve with voltage. The valve is grounded (control stage) in the engine control module (ECM). When the valve is grounded using a pulse width modulation (PWM) signal, the oil flow in the valve can be controlled to the different chambers in the continuous variable valve timing (CVVT) unit at variable rates. This allows the cam timing to be changed precisely and steplessly.
The engine control module (ECM) can diagnose the camshaft reset valve.
The valve is on the cylinder head above the camshaft with camshaft control.

Turbocharger (TC) control valve




The turbocharger (TC) control valve is used to open/close the connection between the intake manifold and the pressure servo for the turbocharger (TC). The valve controls the pressure servo which affects the boost pressure control (BPC) valve and therefore the boost pressure. Also see Function, B5244T5, B5254T2 Function.
The valve is an electro-magnetic valve which is powered from the system relay. When the valve needs to be opened, it is grounded internally in the engine control module (ECM). The valve can be controlled steplessly by grounding the valve using a pulse width modulation (PWM) signal.
The valve is closed when in the standby position (open-circuit).
The turbocharger control valve can be diagnosed and can be activated using VIDA.
The turbocharger (TC) control valve is on a hose between the intake manifold and the pressure servo for the turbocharger.

Ignition coils




The ignition coils supply the spark plugs with high voltage to produce sparks. The engine control module (ECM) controls the ignition coils so that sparks are generated at the correct time.
Each ignition coil has its own integrated power stage.
The ignition coils are in the sparkplug wells above each spark plug.
The ignition coils for each cylinder have different terminals in the engine control module (ECM), depending on whether the engine has 5 or 6 cylinders.
The engine control module (ECM) can diagnose the ignition coils.

Emissions warning lamp




The emissions warning lamp in the Driver Information Module (DIM) has a warning symbol. This warning symbol varies depending on the market and model year. The warning symbols are:
- "Engine symbol" (not USA, model year 2001-)
- "CHECK ENGINE" (MIL - Malfunction Indicator Lamp, USA only).
- "Lambda symbol" (not USA, model year 1999-2000).
The warning symbol lights when the ignition key is turned to position II and goes out when the engine is started if the engine management system does not detect any faults.
The warning lamp is directly connected to the engine control module (ECM).
The warning lamp will light if there is a fault in one of the parameters in the engine management system. The warning lamp will also light in response to a request transmitted via the Control area network (CAN) if there is a fault in one of the following systems which affects emissions:
- transmission control module (TCM)
- brake control module (BCM).