Open Loop

When engine is cold and engine speed is greater than 400 RPM, PCM operates in "open loop" mode. In "open loop", PCM calculates air/fuel ratio based upon inputs from Engine Coolant Temperature (ECT), Intake Air Temperature (IAT) and Manifold Absolute Pressure (MAP) sensors. Engine will remain in "open loop" operation until oxygen sensor reaches normal operating temperature, engine coolant temperature reaches preset temperature, and a specific period of time has elapsed after engine start-up.