Exhaust oxygen sensors are used on Toyota EFI and EFI/TCCS equipped engines to provide air/fuel ratio feedback information to the ECU. This information is used to constantly adjust the air/fuel ratio to stoichiometry during warm idle and cruise operating conditions. The stoichiometric air/fuel ratio delivers one pound of fuel for each 14.7 pounds of air entering the intake manifold and results in the most efficient combustion and catalyst operation. When the electronic control system is using information from the oxygen sensor to adjust air/fuel ratio, the system is said to be operating in closed loop.
Exhaust oxygen sensor efficiency is dependent upon its operating temperature. The sensor will only generate an accurate signal when it has reached its minimum operating temperature of 750'F. Therefore, the oxygen sensor is typically located in the exhaust stream at the manifold collector. This location is close enough to the exhaust valves to maintain adequate operating temperature under most driving conditions and allows a representative exhaust sample from all cylinders.
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