Ignition System: Description and Operation

The ignition system consists of an ignition coil located on each individual cylinder and each individual spark plug. The ignition timing can now be adjusted more rapidly and independently.

The crankshaft position sensor signal is the basis for ignition timing calculations. The alternating voltage signal from the crankshaft position sensor is converted by the powertrain control module (PCM). This digital signal is then used to position the closing time of the primary circuit of the ignition coil. The effective range for ignition timing control is increased to the fact that there are no rotating parts.

On the basis of engine speed and load inputs, the powertrain control module determines the ignition timing. This function also takes other inputs into consideration such as engine temperature, throttle position, knock control and electronic transmission control inputs.

This ignition system enables the customer to drive the vehicle home if a coil failure occurs. In the event of a coil failure the powertrain control module side of the coil would be grounded causing only the defective coil to be isolated from the system, instead of causing the complete engine to be immobilized.