Circuit Description

The ignition control module (ICM) controls spark timing when the engine is cranking. During this Bypass mode of operation, the ICM triggers each ignition coil in the proper sequence at a pre-calibrated timing advance. The ICM is connected directly to the powertrain control module (PCM) and includes the following circuits:

• A low reference circuit
• The low resolution engine speed signal circuit
• The ignition control (IC) timing control circuit
• The IC timing signal circuit

When the PCM begins receiving the 3X reference pulses from the ICM and the engine starts, the PCM applies 5 volts to the IC timing signal circuit. This allows the ICM to switch to the IC mode of operation and spark advance to be controlled by the PCM. The PCM monitors the IC timing signal circuit for errors. If the PCM detects a fault, DTC P1350 sets.