Ford Aerostar 1986-1997 Repair Guide

Oxygen Sensor



See Figure 1

The exhaust gas oxygen sensor supplies the electronic control assembly with a signal which indicates either a rich or lean mixture condition, during the engine operation. This sensor is screwed into the exhaust manifold before the catalytic converter.

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Fig. Fig. 1: Oxygen sensor and wire-heated version


Because of the complexity of the electronic control system and this component, no attempt should be made to repair or test the oxygen sensor. It should only be tested by a qualified mechanic utilizing the correct machines and equipment.

In general, the oxygen sensor is maintenance free, and only requires service during the change interval. Refer to the maintenance schedule for the correct change interval for the vehicle.


See Figures 2, 3 and 4

  1. Disconnect the negative battery cable.
  3. Raise and safely support the vehicle on jackstands.
  5. Locate the oxygen sensor between the exhaust manifold and the catalytic converter.
  7. Disconnect the electrical connector from the sensor. Depending on the production year and electronic control system install on the vehicle, the oxygen sensor could be a two or three wire type. Make sure that all the wires are unfastened.
  9. Spray a commercial solvent onto the sensor threads and allow it to soak in for about 5 minutes.
  11. Carefully remove the oxygen sensor.

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Fig. Fig. 2: Disconnect the oxygen sensor wire harness

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Fig. Fig. 3: Use a suitable wrench to loosen the oxygen sensor

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Fig. Fig. 4: Remove the oxygen sensor from the exhaust tube

To install:
  1. Coat the sensor's threads with an appropriate oxygen sensor anti-seize compound or equivalent. Do not apply the compound too thick. You must coat ONLY the threads with the anti-seize compound.
  3. Install the sensor and tighten to 30 ft. lbs. (39 Nm). Be careful not to damage the electrical connector.
  5. Fasten the oxygen sensor connector.
  7. Connect the negative battery cable.