Function [1 of 4]

Function

Immobilizer
See Design and Function, Immobilizer.

Start (-2005)




The starter motor (6/25) is powered via the starter motor relay (2/35). The relay is controlled by the engine control module (ECM) (4/46). The start process is as follows:
1. The ignition key is turned to start position (position III)
2. A high signal (Ubat) from the ignition switch (3/1) is transmitted to the engine control module (ECM) and starter relay via the central electronic module (CEM) and integrated relay/fusebox in the engine compartment. The engine control module (ECM) interprets this high signal as a request to activate the starter motor.
3. The engine control module (ECM) activates the starter motor solenoid by grounding the relay for the starter motor relay. The relay is powered by the ignition switch
4. The relay closes the circuit between the starter motor solenoid and the fuse in the integrated relay/fusebox in the engine compartment, activating the starter motor
5. The engine control module (ECM) activates the starter motor until the ignition key is released from the start position (position III).
The starter motor will not be activated if:
- the immobilizer function does not permit starting. The engine control module (ECM) receives a signal regarding whether the immobilizer is active or inactive from the central electronic module (CEM) via the control area network (CAN). For more information, See also Design and Function, Immobilizer.
- the gear selector is not in position "P" or "N" (automatic transmissions). The engine control module (ECM) receives a signal indicating the position of the gear selector from the transmission control module (TCM) (4/28) via both the controller area network (CAN) and from 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 clutch pedal is released (manual transmissions, certain markets). The engine control module (ECM) receives a signal indicating the position of the clutch pedal from the central electronic module (CEM) via the controller area network (CAN).

Start (2006-)




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 ignition key is turned to start position (position III)
2. A high signal (U bat ) from the ignition switch (3/1) is transmitted to the engine control module (ECM) via the central electronic module (CEM). The engine control module (ECM) interprets this high signal as a request to activate the starter motor.
3. The engine control module (ECM) activates the starter motor solenoid by grounding and powering the coil for the starter motor relay.
4. 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.
5. 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 ignition key returns to ignition position (position II) before the engine is started, the starter motor continues to run. The starter motor runs until the engine is started or until a certain time has elapsed. The engine temperature dictates the running time of the starter motor:
- at -40 °C, approx. 10 seconds
- at -10 °C, approx. 8 seconds
- over 15 °C, approx. 4 seconds
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" (automatic transmissions). The engine control module (ECM) receives a signal indicating the position of the gear selector from the transmission control module (TCM) (4/28) via both the controller area network (CAN) and from 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 clutch pedal is let up (manual transmission, certain markets). Signal about clutch pedal position goes to Engine control module (ECM) from Central electronic module (CEM) via CAN-net, as well as via a directly connected cable from the clutch pedal switch.

Camshaft control (CVVT)




When the camshaft (A) is set at the factory, it is aligned with the position of the crankshaft (B). The position of the camshaft in relation to the crankshaft is designated the camshaft 0 position. During camshaft (CVVT) control, the 0 position of the camshaft is advanced so that 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.
There are diagnostics for this function. See also: Camshaft diagnostics (CVVT) Camshaft Diagnostics (CVVT)

Detecting the position of the camshaft (camshaft timing changes)




In order to detect the position of the camshaft (camshaft timing) in relation to the crankshaft, the engine control module (ECM) uses the signals from the engine speed (RPM) sensor (the position of the crankshaft) and from the camshaft position (CMP) sensor (the position of the camshaft). The control module uses these two signals to determine the position of the camshaft in relation to the position of the crankshaft.





Detecting the camshaft flanks
The camshaft is divided into four flanks per revolution of the camshaft (flanks 1-4). The flanks are detected by the camshaft position (CMP) sensor. The signal affects the shape of the camshaft rotor. See also: Design Design
The teeth on the camshaft pulse wheel for camshaft flanks 1 and 4 are shorter than the other teeth. This enables the control module to determine the position of the camshaft. The control module is able to establish which combustion cycle the cylinders are in.





Detecting the reference positions of the camshaft
The crankshaft has four reference positions, one for each camshaft flank. The reference positions are predetermined points on the flywheel. The reference positions are detected using the signal from the engine speed (RPM) sensor. See also: Design Design
The camshaft turns at half the speed of the crankshaft. This means that two reference positions are detected for each turn of the crankshaft. Therefore two engine revolutions are required to detect all flanks on the camshaft.
The positions on the flywheel are designated °CA (Crank angle). 0°CA = Top dead center cylinder 1.
Flanks 3 and 4 are detected during the second revolution of the engine.





Detecting the position of the camshaft in relation to the position of the crankshaft
Each camshaft flank aligns with pre-defined positions on the crankshaft when the camshaft is in its 0 position. These positions on the crankshaft are called reference positions for the flanks.
The illustration shows how the signals relate to each other when the camshaft is in its 0 position (the camshaft is not deployed).
A: Engine speed (RPM) sensor signal.
B: Camshaft position (CMP) sensor signal. From high to low signal when the teeth on the camshaft pulley leave the camshaft position (CMP) sensor.
C: Low engine speed (RPM) sensor signal because of the holes in the flywheel/carrier plate.
D: Top dead center (TDC) cylinder 1, 0°CA (84°CA after hole "C" in the flywheel/carrier plate).
1: Detection of flank 1, reference position 47°CA "D1".
2: Detection of flank 2, reference position 227°CA "D2".
3: Detection of flank 3, reference position 407°CA "D3".
4: Detection of flank 4, reference position 587°CA "D4".
If the flanks do not correspond to the reference positions on the crankshaft when the camshaft is in the 0 position (not deployed), the engine control module (ECM) will store the difference. There may be a difference from the camshaft 0 position if the timing belt is incorrectly seated or the camshaft are not correctly set for example. A mechanically damaged camshaft reset valve may prevent the camshaft moving to the 0 position when the engine control module (ECM) stores the adaptation value for the deviation of the camshaft. This may result in high deviation and a diagnostic trouble code (DTC) being stored.
The difference can be read out in VIDA.

Regulating the camshaft position
The engine control module (ECM) controls the camshaft reset valve steplessly. The valve controls the flow of engine oil to the continuous variable valve timing (CVVT) unit which is affected by the oil pressure that builds up. This allows the CVVT unit to change the position of the camshaft. Also see Control (below) and Design Design




When deploying the camshaft by for example 10°CA (the engine control module (ECM) deploys the camshaft), the detection of the camshaft flanks will be offset by 10°CA from the reference positions for the crankshaft.
The illustration shows how the signals relate to each other when the camshaft is controlled (deployed camshaft), D1 - D4 is reduced.
The engine control module (ECM) is then able to calculate the °CA (crankshaft degrees from top dead center (TDC)) that the intake valve opens and the exhaust valve closes for each cylinder. This is because the opening and closing angles are fixed and predefined in relation to the flanks on the camshaft rotor.
The closing angle of the intake valve and the opening angle of the exhaust valve can be read in VIDA.
The following applies when the camshafts are in their 0 position (no deployment):
- the opening angle of the intake valve 27°CA
- the closing angle of the exhaust valve is 26.5°CA.
The following applies when the camshaft is fully deployed:
- the opening angle of the intake valve is -(minus) 23°CA
- the closing angle of the intake valve is -(minus) 3.5°CA.
The total of the closing angle of the intake valve - (minus) the opening of the exhaust valve = the valve overlap.