Basic Control Functions

PGM-FI ECM FUNCTIONS
Injector Discharge Duration
The PGM-FI ECM contains memories for the basic discharge durations at various engine speeds and manifold pressures.
The basic discharge duration, after being read from memory, is further modified by signals sent from various sensors to obtain the final discharge duration.
The most vital of these sensors are: Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Manifold Absolute Pressure (MAP) sensor, Heated Oxygen (HO2S) sensor, and the Barometric Pressure (BARO) sensor.

Ignition Timing
The PGM-FI ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing is also adjusted for coolant temperature.

A knock Control System is also used. If detonation is detected by the Knock Sensor, the ignition timing is retarded.

Idle Speed Control
The idle speed is controlled by the Idle Air Control (IAC) Valve as directed by the PGM-FI ECM, to compensate for various conditions;
^ When the A/C compressor is on.
^ When the transmission is in gear (A/T only).
^ When the alternator is charging.
^ When the power steering is used.
^ Other such conditions which will cause idle speed to change.