Modes Of Operation: Run

When engine is started and speed is above 400 RPM, the system goes into open loop operation. In open loop, ECM will ignore oxygen sensor signals and compute air/fuel ratios based on inputs from coolant and MAP sensors.

The system will remain in open loop until the following conditions are met: oxygen sensor reaches operating temperature, coolant sensor is above a specified temperature and a specific amount of time has elapsed after starting engine.

Specific values for these conditions are stored in the ECM's Programmable Read Only Memory (PROM). When these conditions are met, system will go into closed loop operation. In closed loop, ECM will calculate air/fuel ratio (injector on time) based on oxygen sensor signal, this maintains air/fuel ratio close to 14.7:l.