Description

Engine Ignition

NOTE:
A = Hardwired; D = High speed CAN (controller area network) bus; N = Medium speed CAN (controller area network) bus









Engine Ignition
Each ignition coil contains a power stage to switch the current in the primary circuit. The ECM (engine control module) controls the switching with a signal to the power stage. The ECM (engine control module) monitors operation of the ignition coils using a feedback signal from each of the power stages. If a fault is detected the ECM (engine control module) stores an appropriate fault code.
Power for the ignition coils is supplied from the main relay and a fuse in the BJB (battery junction box). A capacitor is connected in parallel with the power supplies to the ignition coils to suppress RFI (radio frequency interference).
The ECM (engine control module) varies the dwell time of the ignition coils depending on battery voltage and engine speed, to ensure a constant energy level is produced in the secondary coil each time the power stage is switched. This ensures a good spark is always produced by the spark plug without excessive primary current flow, thus avoiding overheating or damage to the ignition coils.
The ECM (engine control module) calculates the ignition timing for individual cylinders from:
- Engine speed
- Camshaft position
- Engine load
- Engine temperature
- The knock control function
- The shift control function
- The idle speed control function.

Ignition Coils
The engine is fitted with eight plug-top coils that are controlled directly by the ECM (engine control module). This means that the ECM (engine control module), at the point where sufficient charge has built up, switches the primary circuit of each coil and a spark is produced in the spark plug. The positive supply to the coil is fed from a common fuse. Each coil contains a power stage to trigger the primary current. The ECM (engine control module) sends a signal to each of the coils power stage to trigger the power stage switching. Each bank has a feedback signal that is connected to each power stage. If the coil power stage has a failure the feedback signal is not sent, causing the ECM (engine control module) to store a fault code appropriate to the failure.
The ECM (engine control module) calculates the dwell time depending on battery voltage and engine speed to ensure constant secondary energy. This ensures sufficient secondary (spark) energy is always available, without excessive primary current flow thus avoiding overheating or damage to the coils.
The individual cylinder spark timing is calculated from a variety of inputs:
- Engine speed and load
- Engine temperature
- Knock control
- Transmission shift control
- Idle speed control.