Modes Of Operation: Notes

As input signals to the PCM change, it adjusts different output devices. For example, the PCM calculates a different injector pulse width for idle than it. does for wide open throttle (WOT). Likewise, the PCM instructs the ICM to change ignition timing to compensate for different engine operating conditions. There are several different modes of operation that determine how the PCM responds to the various input signals.

There are two different areas of operation, Open Loop and Closed Loop. During Open Loop modes, the PCM receives input signals and responds according to preset programming. The inputs from the heated oxygen sensors are not monitored during Open Loop modes.

During Closed Loop modes, the PCM monitors the inputs from the heated oxygen sensors. Oxygen sensor inputs indicate whether or not the calculated injector pulse width results in the ideal air/fuel ratio of 14.7 parts air to 1 part fuel. By monitoring the exhaust oxygen content in each exhaust manifold, the PCM fine tunes injector pulse width. Fine tuning injector pulse width provides optimum fuel economy along with low emissions.

The sequential multi-port fuel injection system has the following modes of operation:

• Ignition Switch On (Zero RPM)
• Engine Start-Up
• Engine Warm-Up Cruise (Idle)
• Acceleration
• Deceleration
• Wide Open Throttle
• Ignition Switch OFF

The engine start-up (crank), engine warm-up, and wide open throttle modes are OPEN LOOP modes. Under most operating conditions, the acceleration, deceleration, and cruise modes, with the engine at normal operating temperatures, are CLOSED LOOP modes.