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Home >> Volvo >> 2007 >> C30 T5 (CANADA) L5-2.5L Turbo VIN 68 B5254T3 >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Relays and Modules - Computers and Control Systems >> Engine Control Module >> Description and Operation >> Function >> Function [4 of 4]

Function [4 of 4]

Ignition control




The following components are used for ignition control:
- engine speed (RPM) sensor (7/25)
- camshaft position (CMP) sensor (7/172-7/173)
- mass air flow (MAF) sensor (7/17)
- engine coolant temperature (ECT) sensor (7/16)
- throttle position (TP) sensor on the electronic throttle unit (6/120)
- knock sensor (KS) (7/24)
- transmission control module (TCM) (4/28)
- spark plugs with ignition coils (20/3-20/7)
- brake control module (BCM) (4/16).
The engine control module (ECM) calculates the optimum ignition advance based on the software and information from the sensors. The engine control module (ECM) cuts the current to the ignition coil mounted on the cylinder to be ignited and produces a spark.
During the starting phase the engine control module (ECM) produces a fixed ignition setting. When the engine has started and the vehicle is being driven, the engine control module (ECM) calculates the optimum ignition setting, taking factors such as the following into account:
- engine speed (RPM)
- load
- temperature.
The engine control module (ECM) analyses the signal from the knock sensor (KS) when the engine reaches operating temperature. If any of the cylinders knock, the ignition is retarded for that specific cylinder until the knocking ceases.
The ignition then advanced to the normal position or until the knock recurs.
Before the transmission control module (TCM) changes gear, it sometimes transmits a torque limiting request to the engine control module (ECM). The engine control module (ECM) then retards the ignition momentarily to reduce the torque, resulting in smoother gear changes and reducing the load on the transmission. There are different ignition retardation levels depending on the signals from the transmission control module (TCM). The return signal from the engine control module (ECM) to the transmission control module (TCM) confirms that the signal reached the engine control module (ECM). The Brake Control Module (BCM) transmits information to the engine control module (ECM) about deviations in the drive line. The signal is used to stop the diagnosis. For further information, also see: Misfire diagnostic Misfire Diagnostics
The engine misfires if the fuel does not ignite correctly. For further information, also see: Misfire diagnostic Misfire Diagnostics

Regulating the air conditioning (A/C) compressor




The air conditioning (A/C) compressor is controlled by the engine control module (ECM) (4/46) on request from the climate control module (CCM) (3/112) via the controller area network (CAN). When the engine control module (ECM) receives a signal from the climate control module (CCM) to activate the air conditioning (A/C) compressor, the engine control module (ECM) grounds the circuit for the relay coil for the A/C compressor. See also: Design, B5244S4 Design
The relay (2/22) closes the circuit between the integrated relay/fuse box in the engine compartment and the clutch for the A/C compressor (8/3).
In addition to the information from the climate control module (CCM), the engine control module (ECM) checks the engagement and disengagement of the A/C compressor based on:
- the signal from the air conditioning (A/C) pressure sensor (high pressure side) (7/8)
- the signal from the air conditioning (A/C) pressure sensor (low pressure side) (8/119)
- the throttle position (TP) sensor (6/120)
- the engine coolant temperature (ECT) sensor (7/16).

Regulating the cruise control




The cruise control function is an example of distributed functionality.
The following components are used when regulating the cruise control:
- engine control module (ECM) (4/46)
- steering wheel module (SWM) (3/254) (cruise control buttons)
- central electronic module (CEM) (4/56) (clutch pedal position)
- brake control module (BCM) (4/16) (brake pedal position, 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).
The driver activates the function by pressing the SET+ or SET- button. A message is then transmitted via the low speed side of the Controller area network (CAN) to the central electronic module (CEM) which then transmits the message on via the high speed side of 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 speed increases as normal and then resumes to the stored value when the driver releases the accelerator pedal (AP) again.
The engine control module (ECM) continually stores the speed. If the cruise control is disengaged, if for example the driver depresses the brake pedal, the previous speed can be resumed by pressing the "RESUME" button.
Cruise control cannot be activated at speeds below 30 km/h.
Cruise control is disengaged:
- when the driver presses the clutch pedal or brake pedal
- when the driver presses the "CRUISE" button on the steering wheel
- when the driver depresses the "0" button on the steering wheel
- if "P" or "N" positions are transmitted on the controller area network (CAN) (applies to automatic transmissions)
- if the speed deviates too much from the set value
- when the control system detects a fault that prevents activation. (For further information, see diagnostic trouble code (DTC) information for the relevant diagnostic trouble codes (DTCs)).

Controlling the generator (GEN) (2005-)




The engine control module (ECM) (4/46) regulates the charge voltage of the generator (GEN) (via LIN communication) when requested by the central electronic module (CEM) (4/56) (via CAN communication).
The engine control module (ECM) can change the charge voltage requested by the central electronic module (CEM). to suit certain operating conditions such as engine start, idle speed or high engine load.
The value requested by the engine control module (ECM) for charging voltage and alternator charging current can be read using VIDA.
The alternator control module (ACM) transmits fault information to the engine control module (ECM). Diagnostic trouble codes (DTCs) are stored in the engine control module (ECM).
For further information about generator (GEN) control, see Design and Function, Generator (GEN) and Design and Function, central electronic module (CEM).
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