Ignition System Operating Modes

Ignition Control Spark Mode

There are two modes of ignition system operation: PCM mode and Ignition Control Module (IC Module) mode. In IC Module mode, the ignition system operates independently from the PCM. The ignition control module maintains a base ignition timing of 10° BTDC and is able to change this ignition timing slightly with increased engine speed. IC 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 PCM mode, the PCM controls the ignition timing. The PCM calculates the desired ignition timing based on information it receives from the input sensors.



PCM Timing Mode

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 (IC Module).

^ Engine Coolant Temperature (ECT) sensor.

^ Manifold Absolute Pressure (MAP) sensor.

^ Transaxle Range (TR) switch.

^ Throttle Position (TP) sensor.

^ Vehicle Speed Sensor (VSS).

^ Knock Sensor (KS).