Run Mode

WARNING: This page is about a different car, the 2003 Saturn LW200 and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.

The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The PCM ignores the signal from the Heated Oxygen Sensor (HO2S) and calculates the air/fuel ratio based on inputs from the ECT, MAF, MAP, and TP sensors. The system stays in Open Loop until meeting the following conditions:

Both HO2S have varying voltage output, showing that they are hot enough to operate properly. This depends upon the engine temperature.
The ECT sensor is above a specified temperature.
A specific amount of time has elapsed after starting the engine.