Hello .. thanks for the doantion .. much apreciated
The PCM, using input signals, determines adjustments to the air/fuel mixture in order to provide the optimum ratio for proper combustion under all operating conditions. One of 2 types of fuel control systems are used: throttle body injection or port fuel injection. These systems can operate in the "open loop" or "closed loop" mode. Description of these modes is as follows:
When engine is cold and engine speed is greater than 400 RPM, PCM operates in "open loop" mode. In "open loop", PCM calculates air/fuel ratio based upon coolant temperature and Manifold Absolute Pressure (MAP) or Mass Airflow (MAF) sensor readings. Engine will remain in "open loop" operation until oxygen sensor reaches operating temperature, coolant temperature reaches preset temperature and a specific period of time has elapsed after engine start-up.
When oxygen sensor has reached operating temperature, coolant temperature has reached a preset temperature and a specific period of time has passed since engine start-up, PCM operates in "closed loop". In "closed loop", PCM controls air/fuel ratio based upon oxygen sensor signals (in addition to other input parameters) to maintain as close to a 14.7:1 air/fuel mixture as possible. If oxygen sensor cools off (due to excessive idling) or a fault occurs in the oxygen sensor circuit, vehicle will once again enter "open loop" mode.
Hope this helps
HAPPY NEW YEAR
Thursday, December 31st, 2009 AT 10:34 PM