Part 1

Function

Start




The starter motor (6/25) is supplied with power via the starter motor relay (2/35), the starter motor relay is controlled by the engine control module (ECM) (4/46).

The start process is as follows:
1. The starter button on the start control module (SCU) is depressed (position III).
2. A high signal (Ubat) from the start control module (SCU) (3/132) reaches the central electronic module (CEM) via LIN communication.
3. The central electronic module (CEM) uses the button signal together with the signal from the stop lamp switch (3/9) and creates a start request that is transmitted to the engine control module (ECM) via CAN communication.
4. The Engine Control Module (ECM) uses the received start request, and the directly connected signal from the start control module (SCU), and activates the starter motor's solenoid by grounding and powering the starter motor relay's coil.
5. The relay closes the circuit between the starter motor solenoid and the fuse in the relay/fuse box in the engine compartment, activating the starter motor.
6. The engine control module (ECM) activates the starter motor until the engine starts (the engine speed (rpm) exceeds a certain value)
Auto start
If the starter button is released before the engine is started, the starter motor continues to run. The starter motor runs until the engine is started or until after a certain amount of time, depending on the engine coolant temperature (ECT). Low temperatures permit longer start times.
If the engine does not turn or if the engine speed is extremely low when the start relay is activated, the engine control module (ECM) interrupts start relay activation.
Activation of the starter motor is not permitted or is interrupted if:
- the engine is running (the engine speed (RPM) above a certain value)
- the immobilizer function does not allow a start. For further information also see Design and Function, Immobilizer
- the gear selector is not in position "P" or "N". The engine control module (ECM) receives a signal indicating the position of the gear selector (P/N engage/disengaged) from the transmission control module (TCM) (4/28), partially via the controller area network (CAN) and partially via a directly connected cable between the engine control module (ECM) and transmission control module (TCM). Also see Design and Function, Transmission control module (TCM).
- The brake pedal is not depressed. The signal about active/inactive brakes is received by the engine control module (ECM), partially from the directly connected stop lamp switch, partially from the brake pedal switch position, which is transmitted from the brake control module (BCM) to the engine control module (ECM).

Camshaft control (CVVT)




Both intake camshafts and exhaust camshafts are regulated by the Engine Control Module (ECM). The intake camshafts are located in the middle of the engine, while the exhaust camshafts are located furthest out. The camshafts are divided into two banks.
Bank 1 (front cylinder row); cylinders 1, 3, 5 and 7.
Bank 2 (rear cylinder row, closest to the passenger compartment); cylinders 2, 4, 6 and 8.
The inlet camshafts are driven primarily by the crankshaft and chain, whilst the exhaust camshafts are driven by a chain from the inlet camshafts.
When each camshaft is set at the factory, it is aligned with the position of the crankshaft. The position of the camshaft in relation to the crankshaft is designated the camshaft 0 position (default setting). During camshaft control (CVVT) the camshaft 0-position is offset so that the cam timing changes. The opening and closing of the intake and exhaust valves can be changed to match the camshaft. Engine performance can be increased, idle quality increased and emissions reduced by regulating the camshaft timing changes.
The engine control module (ECM) detects the position of the camshafts by comparing the signals from the engine speed (RPM) sensor (1) (crankshaft position) and the camshaft position (CMP) sensors (2) (camshaft positions). The engine control module (ECM) then controls the angle of the camshaft by controlling the oil flow to the CVVT unit using the reset valve camshaft (3).
There are diagnostics for this function. See also: Camshaft diagnostics (CVVT) Camshaft Diagnostics (CVVT)

Controlling, reset valve camshaft




1. Oil filter reset valve camshaft.
2. Oil duct (pressure, inlet).
3. Duct leading to CVVT unit chamber (deployment).
4. Duct leading to CVVT unit chamber (deployment).
The camshaft reset valve controls the oil flow to the continuous variable valve timing (CVVT) unit. The engine control module (ECM) uses a pulse width modulation (PWM) signal to control the valve. See also: Design Design

Controlling, CVVT units




The CVVT units are the "Vane" type which means that the CVVT unit rotors are turned by oil pressure on one, or the other, side of the rotor wings.
A. CVVT unit exhaust
B. CVVT unit inlet
1. Timing belt pulley inlet camshaft (primary, inlet camshaft driven by the crankshaft).
2. Timing belt pulley inlet -/exhaust camshaft (secondary, exhaust camshaft driven by inlet camshaft).
3. Oil duct reset valve camshaft (pressure).
4. Oil duct for controlling CVVT unit.
5. Oil duct for return CVVT unit.
6. Spring (CVVT unit exhaust camshaft only).
The continuous variable valve timing (CVVT) unit allows the position of the camshaft to be adjusted relative to the crankshaft.
The camshaft is secured to the CVVT unit rotor. The rotor (and with it the camshaft) rotates in relation to the timing belt pulley (1) by the oil pressure building up on one or both sides of the rotor vanes in the CVVT unit.
The difference in function between the exhaust camshaft (A) and inlet camshaft (B) CVVT unit is that the exhaust camshaft CVVT unit is equipped with a spring. The force of the spring makes the CVVT unit deploy the camshaft. The function causes faster deployment of the exhaust camshaft at engine start-up, before the oil pressure build in the engine.

Control occurs according to the following during deployment/return of the camshaft.




A. Exhaust camshaft
B. Inlet camshaft
- Oil pressure from the lubrication system (1) of the engine.
- The oil passes the filter for the camshaft reset valve (2) and then on to the reset valve (3).
- The engine control module (ECM) controls the oil flow to one of the CVVT unit chambers (4) depending on whether it is to be deployed/returned by the camshaft.
The reset valve is controlled by the engine control module (ECM) by high frequency, switching for deployment and return. This results in rapid and precise control. Both camshafts can be controlled up to 40 crankshaft degrees.

Controlling the generator




The engine control module (ECM) (4/46) regulates the charge voltage of the generator (GEN) (6/26) (via LIN communication) when requested by the central electronic module (CEM) (4/46) (via CAN communication).
The engine control module (ECM) can change the requested charging voltage from the central electronic module (CEM) in order to adapt it to certain operating conditions such as starting, idling or high engine loads.
The value of requested charge voltage from the engine control module (ECM) and the charge current of the generator can be read off.
The alternator control module (ACM) (6/26) transmits information to the engine control module (ECM) regarding any faults). The diagnostic trouble codes (DTCs) are stored in the engine control module (ECM) in the event of a fault. In the event of certain faults, information about these faults is also transmitted to the central electronic module (CEM).
For additional information on regulating the alternator, see Design and Function, Alternator and Design and Function, central electronic module (CEM).

Variable intake system




The variable intake system components consist mainly of:
1. Vacuum tank
2. Valve for variable intake
3. Vacuum motor
4. Throttle discs
In order to maintain a high volume of intake air at different engine speeds (RPM) and engine loads, B8444S is equipped with the Variable Intake System. The Variable Intake System divides drawn in air into two volumes. The engine control module (ECM) then regulates the air flow between these volumes using dampers in order to achieve the optimum air flow at specific operating temperatures.
The vacuum from the engine is stored in a vacuum tank (1). The vacuum is then guided to the vacuum motor (3) using the variable intake valves (2). The vacuum motor affects the damper in the intake system.
The variable intake valve is controlled by the engine control module (ECM) (4/46).
The variable intake valve can be activated and the variable intake function can be diagnosed by the engine control module (ECM).

Oil monitoring




General
The following components are used for oil monitoring:
- oil level-/oil temperature sensor (7/35)
- engine control module (ECM) (4/46)
- driver information module (DIM) (5/1).
The sensor informs the driver via the driver information module (DIM) that the oil needs to be topped up.
Detecting the oil level
The integrated electronics of the sensor calculates the oil level using the measured value for the oil temperature.
For the correct oil level to be calculated, temporary oil level changes in the oil trough must also be included in the calculation, which can occur when driving on hills, around bends or similar for example. The engine control module (ECM) makes these calculations using the oil level sensor signal and a number of other parameters, for example, vehicle speed signal and load signal.

Regulating cruise control (does not apply to adaptive cruise control)





The following components are used when regulating the cruise control:
- engine control module (ECM) (4/46)
- the steering wheel module (SWM) (3/130) (cruise control buttons), communicates with the central electronic module (CEM) via LIN communication.
- brake control module (BCM) (4/16) (brake pedal status, speed signal)
- driver information module (DIM) (5/1) (cruise control lamp)
- transmission control module (TCM) (4/28) (cruise control active/not active, gear selector in position "P" or "N")
- electronic throttle unit (6/120)
- stop lamp switch (3/9).
To activate cruise control the function must be switched on using the "CRUISE" button. A lamp lights up in the driver information module (DIM). Cruise control is then in standby mode.
The driver activates the function by pressing the SET+ or SET- button. A message is then transmitted via LIN communication to the central electronic module (CEM), which then transmits the message on via the Controller area network (CAN) to the engine control module (ECM).
The engine control module (ECM) controls the throttle angle so that a constant speed is maintained using the vehicle speed signal from the Brake Control Module (BCM). The transmission control module (TCM) also receives a message indicating that cruise control is active via the Controller area network (CAN), so that the transmission follows certain shifting patterns when the cruise control is active.
If the accelerator pedal (AP) is depressed the vehicle speed increases as normal and then resumes the stored value when the driver releases the accelerator pedal (AP) again.
The engine control module (ECM) continually stores the speed that is selected using the steering wheel buttons. The stored speed is displayed in the driver information module (DIM).
If the cruise control is switched off, for example, when the driver depresses the brake pedal, the system returns to standby mode. The stored speed is then displayed in the driver information module (DIM) between brackets. The stored speed is resumed by pressing the "RESUME" button. The brackets around the selected speed disappear from the driver information module (DIM).
Cruise control cannot be activated at speeds below 30 km/h.
The cruise control returns to standby mode if:
- the driver depresses the brake pedal
- the driver presses the "CRUISE" button on the steering wheel
- the driver presses the "0" button on the steering wheel
- the gear selector is in position "P" or "N"
- if the speed deviates too much from the set value, for example, by the accelerator pedal (AP) being depressed for a longer time.
- certain diagnostic trouble codes (DTCs), which block continued activation, are stored. (For further information, see the diagnostic trouble code (DTC) information).

Regulating the adaptive cruise control
See Design and Function, Forward Sensing Module (FSM).

Fuel trim





Overview
Fuel trim reduces exhaust emissions. Fuel trim reduces nitrous oxides (NOx), carbon monoxide (CO) and hydrocarbon (HC) emissions.
Theoretically, if the correct amount of oxygen is added during combustion, fuel can be converted to water (H2O) and carbon dioxide (CO2). Emissions would then be completely safe.
In practice considerable amounts of hydro-carbons (HC) and varying amounts of carbon monoxide (CO) and carbon dioxide (CO2) remain.




Due to the high temperature and pressure, nitrous oxides such as NO and NO2 are also formed. The common designation for these gases is nitrous oxides NOx.




By speeding up the reaction between the remaining reactive components using a catalytic converter, these can be converted to water (H2O), carbon dioxide (CO2) and nitrogen (N2).
However this can only happen if the balance of hydro-carbons (HC), carbon monoxide (CO), oxygen (O2) and nitrous oxides (NOx) is exactly right in the exhaust. This happens when the fuel air mixture before combustion is 14.7 kg of air per kg of fuel. The Lambda value is then said to be one, (lambda=1).




A base program in the engine control module (ECM) calculates the injection period based on data about load, i.e. the measured air mass and engine speed (rpm). The calculated injection time (from the base program) is then modified by a circuit (short-term fuel trim). The signal from the heated oxygen sensor (HO2S) is used to finely adjust the injection period so that lambda=1 is reached. The short-term fuel trim is a circuit that finely adjusts the injection period so that the fuel/air mixture is optimized (lambda=1). The control module also used the signals from the front and rear heated oxygen sensors (HO2S) to correct the front heated oxygen sensor (HO2S) (offset adjustment) and thereby the injection period. This gives a higher degree of accuracy during fuel trim. Fuel trim is a rapid process which may take place several times a second. Adjustment of the injection period calculated in the base program is limited.
The short-term fuel trim can be read off.

Adaptive functions




Certain factors, for example, tolerance deviations on certain components such as mass air flow (MAF) sensor and injectors, air leakage on the intake side, fuel pressure etc. affect the fuel / air mix. In order to compensate for this, the engine control module (ECM) has adaptive (self learning) functions. When the engine is new the short term fuel trim varies cyclically around a nominal central line (A) 1.00, with, for example, a ±5% change of injection time when fuel trim is in operation.
If there is air leakage for example, the short-term fuel trim will quickly be offset to a new position (B) and will then work for example between 1.10 (+10%) and 1.20 (+20%), although still at an amplitude of 5%, but with an offset in relation to the original center line (A). The injection period has then been increased to compensate the increase in the amount of air.