Ignition System: Description and Operation

Fig 1 Powertrain Control Module:

POWERTRAIN CONTROL MODULE
The ignition system is regulated by the Powertrain Control Module (PCM) (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 the crank-start period the PCM advances ignition timing a set amount. During engine operation, the amount of spark advance provided by the PCM is determined by the following input factors:

- Available Manifold Vacuum
- Barometric Pressure
- Engine Coolant Temperature
- Engine RPM
- Throttle Position

The PCM also regulates the fuel injection system.

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

IGNITION TIMING PROCEDURE
This engine uses a distributor, crankshaft sensor and ignition coil. The system's main components are the distributor, distributor pickup, camshaft signal, crankshaft signal and ignition coil.