Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Oxygen Sensor


As part of the vehicle's closed loop (or feedback control) system, the oxygen sensor monitors the density of oxygen in the exhaust gas. The sensor consists of a closed-end tube made of ceramic zirconia and other components. Porous platinum electrodes cover the tube's inner and outer surfaces. The tube's outer surface is exposed to the exhaust gases in the exhaust manifold (or, if so equipped, just beyond the turbocharger). After detecting the amount of oxygen in the exhaust gas, the oxygen sensor outputs an electrical signal to the engine control unit.


Gasoline Engines

See Figures 1 and 2

The oxygen sensor is installed in the exhaust manifold (or the front catalytic converter on turbocharged vehicles), and is removed in similar manner to a spark plug. (Unlike spark plug removal, use an open-end wrench to avoid interference with the electrical lead.)

  1. Disconnect the negative battery cable.
  3. Unfasten the sensor's electrical connector.

Click image to see an enlarged view

Fig. Fig. 1: Use an open-end wrench to remove and install the oxygen sensor

Click image to see an enlarged view

Fig. Fig. 2: Handle the oxygen sensor very carefully, be sure not to damage the insulator

  1. Using the correct size wrench, loosen and unscrew the oxygen sensor. If so equipped, be sure to also remove the crush ring gasket with the sensor.

Exercise care when handling the sensor; do not drop or handle it roughly. The electrical connector and louvered end must be kept free of grease and dirt.

  1. Clean the threads of the sensor and its mounting location.

To install:
  1. If applicable, make sure that the crush ring gasket is threaded onto the sensor.
  3. Coat the threads of the sensor with an anti-sieze compound. Be careful to coat only the threads of the sensor; do not get compound on the sensor itself.
  5. Screw the sensor and gasket into its mounting location and torque to specification.
  7. Attach the sensor's electrical connector.
  9. Connect the negative battery cable.