Originally Posted by 94 GT 5.0
Im confused to what this is? Can somebody please explain
When the engine is first started, and rpm is above 400 rpm, the system goes into 'Open Loop' operation. In 'Open Loop', the ECM will ignore the signal from the Oxygen (O2) sensor and calculate the air/fuel ratio based on inputs from the coolant and MAF sensors, but mostly from a pre-programmed table in the memcal.The system will stay in 'Open Loop' until the following conditions are met:1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature)*2. The coolant sensor is above a specified temperature about 40oC/104oF.*3. A specific amount of time has elapsed after starting the engine.The specific values for the above conditions vary with different engines and are stored in the mem-cal. When these conditions are met, the system goes into 'Closed Loop' operation. In 'Closed Loop', the ECM will calculate the air/fuel ratio (injector on-time) based on the various sensors but mainly the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.
I copied and pasted this but its simple. When you cold start your car the secondary air pump turns on till the car is warmed up and is in open loop which means the ecu isn't controlling anything. When the car warms up it switches to closed loop and the ecu is in control of everything. Also when you go wot it switches back to open loop I believe.