System Description

DESCRIPTION
The distributor contains no centrifugal or vacuum advance mechanisms. All spark advance/retard is accomplished electronically by the Powertrain Control Module (PCM).

OPERATION
During engine cranking (and after the engine starts), a hall effect switch inside the distributor assembly sends a variable, Profile Ignition Pickup (PIP), voltage signal to the Ignition Control Module (ICM), which is mounted on the left fender wall, and to the PCM, which uses it to determine crankshaft position and engine speed.

Using the signal and information provided by other engine control sensors, the PCM determines the appropriate ignition timing. The PCM then sends a Spark Output (SPOUT) timing signal back to the ICM.

The ICM turns the ignition coil primary circuit "ON" and "OFF", according to the SPOUT signal from the PCM. Each interruption of the ignition coil primary circuit causes the ignition coil secondary circuit to produce an open circuit high voltage pulse of up to 40,000 volts. These high voltage pulses are routed to the distributor, which sends them to the spark plugs.

The PCM monitors the ICM's control of the ignition coil through the Ignition Diagnostic Monitor (IDM) circuit.

If the ICM does not receive a SPOUT signal from the PCM, the ICM will set timing at a fixed value.