LW2 V6-3.0L VIN R (2000)
Engine Control Module: Description and Operation
Open and Closed Loop Operation
The ECM operates in two different fuel control modes: Open Loop and Closed Loop. Whenever the vehicle is first started the ECM operates in open
loop fuel control. When the ECM determines that the engine oxygen sensor has reached the appropriate temperature, it will go into closed loop fuel
control operation. Closed loop fuel control operation will be maintained as long as certain parameters are met.
In closed loop fuel control, the ECM varies the fuel to the engine according to signals received from the oxygen sensor, located in the exhaust manifold.
The oxygen sensor sends a lambda signal to the ECM indicating the oxygen content of exhaust gases. If the oxygen sensor signals that the air/fuel
mixture is lean, the ECM will increase the amount of fuel to the engine. If the oxygen sensor signals that the air/fuel mixture is rich, the ECM will
decrease the amount of fuel to the engine. During closed loop fuel control operation, the ECM is constantly adjusting the amount of fuel to the engine,
according to signals received from the oxygen sensor, in order to obtain a 14.7:1 air/fuel ratio.
If there are any oxygen sensor related diagnostic trouble codes or if the oxygen sensor does not switch between rich and lean, the ECM will not go into
closed loop fuel control operation.
