Part 2

Design

Engine speed (RPM) sensor




The engine speed (RPM) sensor provides the Engine Control Module (ECM) with information about the speed and position of the crankshaft. The engine control module (ECM) is able to use the signal from the engine speed (RPM) sensor to determine when the piston in cylinder 1 is approaching top dead center (TDC). However it is unable to use the signal from the engine speed (RPM) sensor to determine whether the piston is in the combustion stroke or whether the exhaust valve is open (exhaust stroke). The signal from the camshaft position (CMP) sensor is also required to determine the operating cycle of the engine.
The signal from the engine speed (RPM) sensor is also used to check the engine for misfires. For more information, see: Misfire diagnostic Misfire Diagnostics
There is a steel ring with stamped holes welded to the rim of the primary section (the section fixed to the crankshaft) of the flywheel.
The holes are positioned with a gap of 6° between each hole. This arrangement creates a hole for each tooth. There are 360° in one revolution. 6° between each hole means that there are 60 holes. However two holes are not stamped, to create a reference position (long gap - missing tooth) for the crankshaft. The first tooth after the reference position is located 84° before TDC on cylinder 1. See: Function, B5254T7 Function
The engine speed (RPM) sensor is at the rear of the engine above the flywheel.
The sensor is inductive with a permanent magnet. An alternating current is induced in the sensor when the flywheel/carrier plate passes the engine speed (RPM) sensor. The generated voltage and frequency increases with the engine speed (rpm).
The signal varies between 0.1-100 V depending on the engine speed (RPM).
The Engine Control Module (ECM) is able to determine the engine speed (RPM) by counting the number of holes per time unit. When the reference position passes the engine speed (RPM) sensor, the voltage and frequency drop momentarily to zero, even though the engine is still running. This allows the engine control module (ECM) to determine the position of the crankshaft.
If the signal from the engine speed (RPM) sensor is incorrect or missing, the control module will use the signals from the camshaft position (CMP) sensor, on the condition that the position of the camshaft has been adapted. This means that the car can be driven if the signal is missing.
The engine control module (ECM) can diagnose the engine speed (RPM) sensor. The sensor value (engine speed (rpm)) can be read off using VIDA.

Fuel pressure sensor / fuel temperature sensor




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.
The fuel pressure sensor is on the right-hand end of 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. See also: Function, B5254T7 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 fuel density.

Camshaft position (CMP) sensor




The function of the camshaft position (CMP) sensor is to detect the flanks of the camshaft rotor. The signal from the sensor is used by the engine control module (ECM) to determine the angle of the camshaft.
Each camshaft has four segments per camshaft revolution. A pulse wheel on the camshaft consisting of four teeth (the teeth are positioned by each flank) is used by the camshaft position sensor (CMP) to detect the segments.
The teeth on the camshaft gear wheel are not equally wide. This allows the control module to determine which flank is detected and therefore which operating cycle the camshaft is in.
When the operating cycle of the camshaft is established, the control module is able to determine which cylinder should be ignited. In the event of misfire or knock in the engine, the control module is also able to determine which cylinder is misfiring or knocking. See also: Knock sensor (KS) and Engine speed (RPM) sensor
Data about the position of the camshaft is used during camshaft control (CVVT). See also: Function, B5254T7 Function
The sensor, which is a magnetic resistor with a permanent magnet, is grounded in the control module and supplied with 5 V from the control module. When one of the teeth on the camshaft pulse wheel passes the camshaft position (CMP) sensor, a signal is transmitted to the control module from the camshaft position (CMP) sensor. The signal varies between 0-5 V and is high when a tooth is in contact with the camshaft position (CMP) sensor and low when the tooth leaves the camshaft position (CMP) sensor.
The camshaft position (CMP) sensor is positioned at the rear of the engine by the controllable camshaft (CVVT).
The engine control module (ECM) can diagnose the camshaft position (CMP) sensor.

Knock sensor (KS)




The function of the knock sensor (KS) is to monitor combustion knocking from the engine. Knocking may damage the engine and reduces the efficiency of engine combustion.
If the engine control module (ECM) registers knocking from any of the cylinders, the ignition will be retarded for that cylinder at the next combustion stage. If repeated ignition retardation does not prevent knocking, the injection period will be increased. This has a cooling effect. On turbocharged engines the boost pressure will also be lowered, reducing the engine load.
The sensor is made up of a piezo electrical crystal. If there is engine knock, vibrations (sound waves) spread through the cylinder block to the knock sensor (KS). The resultant mechanical stress in the piezo electrical material in the knock sensors generates a voltage. This signal is transmitted to the Engine Control Module (ECM). The signal corresponds to the frequency and amplitude of the sound waves. This allows the Engine Control Module (ECM) to determine if the engine is knocking. The camshaft position (CMP) sensor and engine speed (RPM) sensor are used to determine the operating cycle of the engine (which cylinder is igniting) and therefore which cylinder is knocking.
The knock sensors (KS) are positioned on the cylinder block below the intake manifold.
Ignition retardation due to knocking can be read using VIDA.
The engine control module (ECM) can diagnose the knock sensors (KS).

Electronic throttle unit




The electronic throttle unit, using the control signal from the engine control module (ECM), regulates the amount of air for engine combustion. This is done using an electronic shutter.
The electronic throttle unit consists of a round throttle disc on a shaft. This is turned using a DC motor (damper motor), gear wheel and two springs, an opening spring and a return spring. The damper motor is controlled by the control module and is supplied with powered by a built in power stage in the control module. At one of the limit positions the throttle disc is closed so that no air can pass the throttle unit. At the other limit position the throttle disc is parallel to the air flow so that the air is able to freely pass through the throttle unit. The throttle disc shaft is mechanically connected to two built-in potentiometers (position sensors) which are supplied with power by the control module. The signals from the potentiometers provide the control module with data about the position of the throttle disc. The throttle unit also has a connector with six gold plated terminal pins.

Note! A damaged pin surface can interfere with the function.

1. Current channels, potentiometers
2. Contact strips, potentiometers
3. Spring
4. Spring
5. Throttle disc
6. Damper motor
7. Gear wheel
8. Gear sector
9. Connector
The throttle unit is located on the engine intake manifold.
In the event of a fault, the throttle unit must be replaced as a single unit.
The engine control module (ECM) can diagnose the electronic throttle unit.

Throttle position (TP) sensor
See Electronic throttle unit

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 sensor consists of a plastic housing with two potentiometers, an AC/DC 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 analog and a digital signal (pulse width modulated (PWM) signal). The signals give information about the position of the accelerator pedal (AP). The digital signal is generated by the AC/DC converter in the sensor and is transmitted to the engine control module (ECM). The analog signal is transmitted central electronic module (CEM) and on to the engine control module (ECM) via the controller area network (CAN). The analog and digital signals are used at the same time by the engine control module (ECM) to regulate the throttle shutter angle.
The sensor is supplied with 12 V by the system relay via a fuse 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. The accelerator pedal (AP) position sensor signals can be read off using VIDA. 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.

Clutch pedal switch




Engine control module (ECM) receives information about the clutch pedal's position in two ways.
Partly from a clutch pedal position sensor which is directly connected to Central electronic module (CEM), and partly from a clutch pedal switch directly connected to the Engine control module (ECM).
The function of the clutch pedal switch is to provide extra safety for the function autostart. In order for the function to be activated, the Engine control module (ECM) must receive signal that indicates pressed down pedal from the clutch pedal switch.
To start without the function autostart it is enough that any of the signals (from clutch pedal position sensor or clutch pedal switch) indicates pressed down pedal.
For more information about the clutch pedal position sensor, see Design and Function, central electronic module (CEM).
In its starting position, the clutch pedal switch is open (clutch pedal released). The switch's installation shall be adjusted so that is is closed when the clutch pedal passes 75% of full pedal movement.
The clutch pedal switch is on the pedal box by the clutch pedal.
The engine control module (ECM) can diagnose the clutch pedal switch. The status (position) of the switch can be read using the diagnostic tool.

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/fusebox in the engine compartment and is diagnosed by the engine control module (ECM).

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
See Design and Function, central electronic module (CEM).

Starter motor relay




The function of the starter motor relay is to supply power to the starter motor. See also Function, Start
The starter motor relay is in the relay/fusebox in the engine compartment.

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 by grounding the valves in pulses.
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 and 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 drained (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. A pulse width modulation (PWM) signal is used to ground the valve and to control the degree to which the valve will open. In this way, the drainage of the EVAP canister is matched to the volumetric efficiency of the EVAP canister, the engine speed (RPM) and the engine load.
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 camshaft timing changes). The direction in which the camshaft turns depends on the chamber in the CVVT unit which is supplied with oil (pressure). See also: Function, B5254T7 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 regulated to the different chambers in the continuous variable valve timing (CVVT) unit at variable rates. This allow the angle of the camshaft to be changed precisely and smoothly.
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 and 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. See also: Function, B5254T7 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 bracket by 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 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. The warning symbols are:
- Engine symbol" (not USA)
- "CHECK ENGINE" (MIL - Malfunction Indicator Lamp, USA only)
The warning lamp lights when the ignition key is turned to position II. The warning lamp will go out after approximately 15 seconds or if the engine is started when no fault is found in the engine management system.
If Readiness is not complete (certain diagnostic functions not completed), the warning lamp will flash instead of going out when the ignition key is in position II.
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 the transmission control module (TCM) which affects emissions.