Pontiac Fiero 1984-1988 Repair Guide

Oxygen Sensor (O


The exhaust oxygen sensor is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gases. The oxygen reacts to the oxygen sensor to produce a voltage output. The voltage ranges from .1 volts for lean mixtures to .9 volts for rich mixtures.

The oxygen sensor uses a permanently attached pigtail and connector. This pigtail should NOT be removed from the sensor. Damage to the oxygen sensor will result.


Click image to see an enlarged view

Fig. Fig. 1 Exploded view of the oxygen sensor is mounting on the 2.8L engine

Click image to see an enlarged view

Fig. Fig. 2 The oxygen sensor is located in the exhaust manifold on the 2.5L engine

The oxygen sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive force may damage the threads in the exhaust manifold or cross-over pipe.

  1. Disconnect the negative (-) battery cable.
  3. Disconnect the electrical connector at the plug.
  5. Remove the sensor from the exhaust manifold or crossover pipe, being careful not to damage the manifold threads.

A special anti-seize compound is used on the oxygen sensor threads to prevent thread seizure. The threads MUST be coated with anti-seize compound No. P/N 5613695 or equivalent before installation.

To install:

  1. Position the sensor and seal into the exhaust manifold. Torque the sensor to 30 ft. lbs (41 Nm) and connect the electrical connector. Reconnect the negative battery cable and start the engine to check for exhaust leaks.