Run Mode

The ``run'' mode consists of two separate operating conditions; open loop and closed loop.
The system goes into open loop operation when the engine is first started and engine speed is above 400 RPM. In open loop mode operation, the ECM disregards oxygen sensor signal and determines air/fuel mixture primarily on inputs from the coolant and MAP sensors. The system will remain in open loop operation until the oxygen sensor has varying voltage output and is hot enough to operate, or the coolant sensor is above 158° F and 60 seconds has elapsed after starting the engine. When these conditions are met, the system switches to closed loop operation.
In the closed loop mode of operation, the ECM calculates the air/fuel mixture based on signals from the oxygen sensor. This allows the air/fuel mixture to stay close to the optimum 14.7:1 ratio.