Part 2

Design

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. They are also pre-heated to ensure that the heated oxygen sensors (HO2S) maintain a normal operating temperature and to prevent condensation which could damage the heated oxygen sensor (HO2S).
The sensor's heating coil consists of a PTC-resistor. The heating coil is supplied with voltage from the system relay and is grounded internally in the Engine control module (ECM).
When the control module grounds the connection, a current will pass through the PTC-resistor. When the heated oxygen sensor is cold, the resistance in the PTC-resistor is low and a high current will pass through the circuit. To avoid condensation damage to the heated oxygen sensor the current is pulsed from the Engine control module (ECM) in the beginning. Depending on the temperature, consideration is given to dew point and, as the temperature increases in the PTC-resistor, the resistance increases in the resistor, the current is reduced and transfers gradually to non-pulsing current.
The heating period for the front heated oxygen sensor is short, approx. 20 seconds.
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 task of the stop lamp switch is to provide the engine control module (ECM) with information about the position of the brake pedal.
When the brake pedal is pressed down, a signal is sent to the Engine control module (ECM) which turns off the cruise control (if it is activated). The brake pedal switch position (connected to the brake control module (BCM)) also handles the function for switching off the 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 stop lamp switch. The status (position) of the switch can be read using the diagnostic tool.
The brake light 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. See also
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.

Accelerator pedal (AP) position sensor




The function of the accelerator pedal position sensor is to provide the engine control module (ECM) and central electronic module (CEM) information on the position of the accelerator pedal. The engine control module (ECM) uses this data to deploy the shutter in the throttle unit to the correct angle.
The accelerator pedal 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 output signals are a pulse width modulated (PWM) signal and an analog signal related to the accelerator pedal (AP) position.
These signals indicate the position of the accelerator pedal (AP). The pulse width modulation (PWM) signal is transmitted to the engine control module (ECM). The analog signal is transmitted to the central electronic module (CEM) and on to the engine control module (ECM) via the controller area network (CAN).
Normally the pulse width modulation (PWM) signal is used to regulate the throttle angle. In the event of a fault in the pulse width modulation (PWM) signal the analog signal is used as a replacement, unless this is also diagnosed as faulty.
The sensor is supplied with 12 V by the system relay via a fuse and is grounded to the body.
The PWM-signal is used together with the analog signal for diagnostics of the accelerator pedal position sensor.
The accelerator pedal (AP) position sensor's signals can be read out with the diagnostics tool. If the Engine control module (ECM) detects a difference between analog and PWM-signal, a diagnostic trouble code is generated and the Engine control module (ECM) then uses the signal with lowest value for control.
The accelerator pedal (AP) position sensor is located on the accelerator pedal bracket.

Oil level and oil temperature sensor




The sensor is a combined oil level and oil temperature sensor. The function of the sensor is to provide the engine control module (ECM) with information about the level and temperature of the engine oil in the oil trough.
The sensor consists of:
- a terminal with three pins
- integrated electronics
- 2 capacitive gauge elements
- a PTC resistor.
The sensor is supplied with 5 V from the engine control module (ECM) and generates a pulse width modulation (PWM) signal to the engine control module (ECM).
The engine control module (ECM) can diagnose the sensor.

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 starter button on the start control module (SCU) has been activated 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).

Fuel 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 along the intake pipe.
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.

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. The signal reconnects to the engine control module (ECM) so that diagnostics can be carried out.
Each ignition coil has an integrated power stage.
The ignition coils are in the sparkplug wells above each spark plug.
The control module checks the ignition coils' function using one separate diagnostic lead.

Camshaft reset valve (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
An oil filter is mounted at the intake channel for the valves to prevent oil contaminants from affecting the function of the reset valves.
The system relay supplies the reset valve with voltage via a fuse. The valve is grounded (control stage) internally 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 allows the angle position to be changed precisely and steplessly.
The engine control module (ECM) can diagnose the camshaft reset valve.
The valve is located on the cylinder head above the camshaft. There is a valve for intake camshaft.
There is no valve for the exhaust camshaft.

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 electromagnetic valve and 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 evaporative emission system (EVAP) valve can be diagnosed by the engine control module (ECM) and can be activated.
The EVAP-valve is located under the manifold (on the front of the engine).

Leak diagnostic unit (certain markets only)




The leakage diagnostic unit's function is to pressurize the tank system for leakage diagnostics.

The leak diagnostic unit consists of a plastic housing with:
1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. a heater element (PTC resistor) which warms up the pump.
The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).
When leakage diagnostics is not active, the valve is kept open to ambient air so that EVAP-control can be performed.
At leakage diagnosis, the pump in the leakage diagnostic unit will start, and the valve in the leakage diagnostic unit will be controlled by Engine control module (ECM) by grounding the various circuits internally in Engine control module (ECM).
Engine control module (ECM) checks sealing in the fuel tank system by pressurizing the system and at the same time monitor a number of relevant parameters. See also: Leak diagnostics (certain markets only), B6304T4 Leak Diagnostics (Certain Markets Only)
The engine control module (ECM) can diagnose the leak diagnostic unit.
The valve in the leakage diagnostic unit can be activated.
The leak diagnostic unit is at the upper front edge of the fuel tank.

air conditioning (A/C) compressor.




The air conditioning (A/C) compressor transports refrigerant, which is necessary for air conditioning (A/C) operation. It is an axial piston compressor with variable displacement. I.E. The compressor has adjustable cylinder displacement which is controlled by a check valve (solenoid). The valve, which is underneath the compressor, can be replaced.
The A/C compressor is mounted on the cylinder block and is driven by the engine's crankshaft via the auxiliaries belt.
For further information, see Design and Function, climate control module (CCM).

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 / opening 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 CAN network from the climate control module (CCM) to activate the relay and start the compressor.

Starter motor relay




The function of the starter motor relay is to supply power to the starter motor. See also
The starter motor relay is in the relay/fuse box in the engine compartment.

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





Note! The engine cooling fan may have a post-run of up to approx. 6 minutes after the engine has been turned off. The time for the fan's post-run depends on engine temperature, temperature in the engine compartment and pressure level in the A/C-system.

Warning! Be careful since the engine cooling fan may have a post-run after the engine has been turned off.

The engine cooling fan (FC) consists of two fans and two control modules. The control modules are controlled by the same signal from the engine control module (ECM).

Hint: For different reasons, there are variants where the engine cooling fan consists of two fans and one control module.

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 modules. The control modules then activate the fans at different speeds. The speed is determined by the engine control module (ECM), depending on the coolant temperature 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) is located behind the radiator and its control module is grounded and powered with battery voltage via a fuse.
There are diagnostics for the engine cooling fan (FC). The engine cooling fan (FC) transmits a diagnostic signal to the engine control module (ECM).

Fuel pump




The fuel pump consists of:





The function of the fuel pump is to ensure that the correct pressure and glow is maintained at the fuel rail on the request of the engine control module (ECM).
The fuel pump is electrically powered via the Pump Electronic Module (PEM) with variable outputs to supply varying fuel pressure/flow and is grounded in the body via the fuel pump control module.
The engine control module (ECM) can diagnose the fuel pump function for the correct pressure and electric open circuit. The fuel pump control module is diagnosed by Engine control module (ECM). See also: Fuel pressure control, diagnostics, B6304T4 Fuel Pressure Control, 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.