Camry CE Sedan 4-Door L4-2164cc 2.2L DOHC MFI (1997)
Heated Oxygen/Air Fuel Sensor: Description and Operation
With California Emissions
Oxygen Sensor Cut-Away
Air/Fuel Sensor Output Voltage Chart
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for the most
efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric
air-fuel ratio.
The A/F sensor has the characteristic that provides output voltage approximately proportional to the existing air-fuel ratio. The A/F sensor output
voltage is used to provide feedback for the ECM to control the air-fuel ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time
immediately. If the A/F sensor is malfunctioning, ECM is unable to perform accurate air-fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is
low (the temp. of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.