ECM/PCM Control of Ignition

The ECM is responsible for maintaining proper spark advance and fuel injection timing for all driving conditions.
To provide optimum driveability and emissions, the ECM monitors input signals from the following components in calculating Ignition Control (IC) timing:

^ Ignition control module.
^ Engine coolant temperature sensor.
^ Mass air flow sensor.
^ Park/neutral position switch.
^ Knock sensor.
^ Throttle position sensor.
^ Vehicle speed sensor.

Under 400 RPM, the ECM will start injector timing as soon as the ignition control module receives a Sync-Pulse" signal, synchronizes the spark and produces a reference signal for the ECM to calculate the fuel ignition timing. The ignition control module controls the ignition timing during this period. Over 400 RPM, the ECM controls ignition timing.