Circuit Description

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The Powertrain Control Module (PCM) supplies Ignition Control (IC) signals to the Ignition Control Module (ICM). The ICM fires the correct ignition coil at the correct time based on the IC signals. The ICM detects if cylinder 1 or cylinder 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil. The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. The ICM provides a synthesized cam signal to the PCM based on these inputs. This is called compression sense ignition. The PCM uses the cam signals to synchronize fuel injection.

This system consists of the following circuits:

Ignition 1 voltage.
Ground.
Camshaft Position (CMP) sensor signal.
IC timing control - 2/3.
IC timing control - 1/4.