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. See also: Knock sensor (KS)
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.
The engine misfires if the fuel does not ignite correctly.