Run Mode

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 control module ignores the signal from the heated oxygen sensor (HO2S). The control module calculates the air/fuel ratio based on inputs from the ECT, MAP, MAF, and TP sensors. The system stays in Open Loop until meeting the following conditions:

• The HO2S has varying voltage output, showing that the HO2S 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.

Specific values for the above conditions exist for each different engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system starts to work in closed loop when these values have been achieved. In closed loop the engine control module calculates the fuel mixture and the injectors' activation time based on the signals from different sensors but mainly from HO2S. This makes it possible to maintain the ratio between air/fuel very close to 14.7:1.