Toyota 89467-41020 Air Fuel Ratio Oxygen Sensor

On the 2007 and the later model, the air/fuel sensors are in the exhaust manifold while the oxygen sensors are down in the exhaust pipes. To do this, place the pins into the signal and the ground terminal without having to remove the electrical connector. Check the voltage signal on a voltmeter, always being wary of hot components, especially the exhausts. The oxygen sensor should first of all, give a steady voltage of 0.1 volts to 0.2 volts when the system is cold and secondly should give fluctuating voltage of 0.1 volts to 0.9 volts when the engine is hot. In the event that closed loop mode is not engaged, then switching is inevitable and replacement called for. Check oxygen sensor heater and to do it measure the resistance on the HT and B+ terminals and check for the battery voltage on the heater. If any of the tests show failure, it means, the sensor has to be replaced. For replacement, first unplug the negative terminal on the battery and if replacing the downstream sensor the passenger seat will be needed to be unbolted and the connector removed. Lift the vehicle if necessary for the replacement of upstream sensor, disconnect the sensor connector then undo the sensor with slotted screw at the exhaust manifold or pipe. Copper anti-seize grease must be applied onto threads before fixing the new or the reinstalled sensor and join the electrical connector, and then lower the vehicle and take a test drive to check the absence of any check engine light. Plug the air/fuel sensor connector: Start the engine and turn on ADM; connect the LED display to the printer After performing above test, check next test suggested for; Air/fuel sensor: For the heating element resistance remove the connector and measure between terminal B+ and HT. If the resistance is incorrect, replace the sensor can be prescribed depending on the circumstances. The method of replacement is similar to the oxygen sensor by which we ensure to apply anti-seize compound and properly connect the electrical connector then jack down the car and check whether there are any check engine codes.

The air/fuel sensor cannot be checked for voltage without a special tool, but the resistance of the heating element can be checked with an ohmmeter.

The PCM responds to the sensor signals by constantly altering the pulse width of the fuel injectors to maintain an air-to-fuel mixture ratio of 14.7 to 1 at all times.

The PCM will set a diagnostic trouble code if this condition occurs at 1,500 or more rpm after the engine reaches normal operating temperature.

The purpose of On-Board Diagnostics II (OBD-II) engine management systems in vehicles is to verify the accuracy of the basic feedback loop between the oxygen sensor and the PCM.