Ignition System: Description and Operation

Fig. 1 Spark Plug Cable Routing:

NOTE: This vehicle uses a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the Powertrain Control Module (PCM).

The PCM regulates the ignition system Fig. 1. The PCM supplies battery voltage to the ignition coil through the Auto Shutdown (ASD) Relay.

The PCM also controls the ground circuit for the ignition coil. By switching the ground path for the coil on and off, the PCM adjusts ignition timing to meet changing engine operating conditions.

During engine operation the following inputs determine the amount of spark advance provided by the PCM.
- Intake air temperature
- Coolant temperature
- Engine RPM
- Intake manifold vacuum
- Knock sensor

The distributorless ignition system used is referred to as the Direct Ignition System (DIS). Basic ignition timing is not adjustable. The system's three main components are the coil pack, crankshaft position sensor, and camshaft position sensor.

The crankshaft position sensor and camshaft position sensor are hall effect devices. The camshaft position sensor and crankshaft position sensor generate pulses that are inputs to the PCM. The PCM determines crankshaft position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft position.