Description And Operation: Operation

The ignition coils are supplied with electrical power from the ECM relay in the EJB (engine junction box). The ECM controls the operation of the ECM relay.

The ECM sends a separate signal to each ignition coil to trigger the power stage switching. The ECM calculates the dwell time from the 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 sufficient spark energy is available without excessive primary current flow, which avoids overheating and damage to the ignition coils.

The ECM calculates the ignition timing for individual cylinders from:

• Engine speed from the CKP (crankshaft position) sensor.
• Camshaft position from exhaust and intake CMP (camshaft position) sensors.
• Engine load.
• Engine temperature.
• The knock control function.
• The shift control function.
• The idle speed control function.