Ignition System: Description and Operation

Ignition System

• All engines use a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the powertrain control module.

The 4.0L engine is a coil on plug design. The systems main components are the ignition coils, crankshaft position sensor, camshaft position sensor and spark plugs.

The CKP and CMP sensors are hall effect devices. The CMP and CKP sensors generate square wave pulses that are inputs to the PCM. Refer to => [ Camshaft and Crankshaft Position Sensor Operation ] Camshaft and Crankshaft Position Sensor Operation. The PCM determines engine position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft and camshaft position.