Circuit Description

Each ignition coil supplies secondary voltage to a pair of spark plugs. This is called a waste spark ignition system. The Engine Control Module (ECM) 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 higher voltage is on the compressing cylinder. The ICM provides a synthesized cam signal to the ECM based on these inputs. This is called compression sense ignition. The ECM uses the cam signals to synchronize fuel injection. This system consists of the following circuits:

• The ignition 1 voltage circuit.
• The ground circuit.
• The Camshaft Position (CMP) sensor signal circuit.
• The IC timing control B 2/3 circuit.
• The IC timing control 1/4 circuit.