Open Loop
WARNING: This page is about a different car, the 2005 Chevrolet Optra5 and 2005 Chevrolet Optra. However, it is still accessible from the selected car via links, so may be relevant.
When the engine is first started and it is above 400 RPM, the system goes into open loop operation. In open loop, the ECM ignores the signal from the O2S and calculates the air/fuel ratio based on inputs from the ECT sensor and the MAP sensor. The ECM stays in open loop until the following conditions are met:
- The O2S has a varying voltage output, showing that it is hot enough to operate properly.
- The ECT sensor is above a specified temperature.
- A specific amount of time has elapsed after starting the engine.