The oxygen sensor is mounted in the exhaust manifold and its function is to measure the oxygen content of the exhaust gas stream and to produce an output voltage in the range 0.1 volt to 0.9 volts where a low voltage corresponds to a high oxygen concentration, or rich mixture, to a low voltage corresponding to a low oxygen concentration, lean mixture. The ECM uses this variable voltage to adjust the particulars of the fuel-to-air mixture with an ideal balance of 14.7 air to 1 fuel in order to obtain the least exhaust emission and optimized
Catalytic Converter functioning. The sensor does not generate voltage below the typical operating temperature of about 600-degrees F, so the ECM runs in open-loop during warm-up. If the engine stays normal temperature and the sensor provides a constant voltage of 0.35 to 0.55 volt, and the TPS shows it is not at idle a Code 13 is stored. A failure to operate for two minutes or more or low voltage or short circuit produces the Code 44, while a high voltage signal produces the Code 45. In these case the ECM drops out to a preset value to fuel delivery rather than using feedback from the sensor. For correct operation of the sensor, its electric contacts have to be clean and well-connected to enable electricity flow, there has to be a proper air circulation around the sensor so that the operating temperature is reached and the fuel used contains no lead. Several precautions should not be made during servicing among them being, do not remove the permanently attached pigtail and connector, do not allow contaminants to come near the electrical connector and the sensor end, do not clean with solvents, handle the sensor tenderly and ensure that the silicon boot is well placed. when replacing the sensor it may be tight if the engine is cold and can be eased if the engine is run for a bit. The procedure includes removing the battery, lifting the car, removing the electrical connector, capturing the position of the silicone boot, unscrewing the sensor loosely, applying some anti seize compound on the threads of the sensor, putting the new sensor and tightening it, connecting the electrical connector, grounding the car and reconnecting the battery.