Circuit Description

The Ignition Control Module (ICM) has independent power and ground circuits. The circuits between the ICM and the Powertrain Control Module (PCM) consist of the following circuits:

• The IC timing signal.
• The IC timing control.
• The low-resolution engine speed signal.
• A low reference signal.

The ICM sends 3X signals to the PCM. The ICM controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions:

• The PCM receives the second 3X signal.
• The PCM applies 5 volts to the IC timing signal circuit.