Signals, Interfaces and Shields

The Powertrain Control Module (PCM) controls spark advance and fuel injection for all driving conditions. The PCM monitors input signals from the following components as part of its ignition control function to determine the required ignition timing:

^ Ignition Control Module (ICM).
^ Engine Coolant Temperature (ECT) Sensor.
^ Manifold Absolute Pressure (MAP) Sensor.
^ Transaxle Range (TR) Switch.
^ Throttle Position (TP) Sensor.
^ Vehicle Speed Sensor (VSS).

MODES OF OPERATION
There are two modes of ignition system operation; MODULE MODE and IGNITION CONTROL MODE. In MODULE MODE, the ignition system operates independently from the PCM. In the MODULE MODE, the ICM maintains the base ignition timing and is able to change this ignition timing slightly with increased engine speed. MODULE MODE is in effect whenever an ignition control fault is detected while the engine is running and it will have a noticeable effect on driveability. In IGNITION CONTROL MODE, the PCM controls the ignition timing. The PCM calculates the desired ignition timing based on information it gets from its input sensors and sends it to the ICM for the execution.