Cadillac 12657188 Oxygen Sensor

An oxygen sensor is a galvanic battery that produces a current output proportional to the oxygen concentration in exhaust gases; it supplies the PCM with essential feedback to sustain the air/fuel equimolar of 14.7:1 to optimise operation of catalytic converter. On-Board Diagnostics II (OBD-II) engine management system fitted vehicles utilise two oxygen sensors, one pre and post catalytic converter to compare the efficiency of oxygen levels in the exhaust gas. All the models have four heated oxygen sensors, namely, cylinder bank sensors located on the exhaust pipe assembly and under the vehicle, each containing an upstream and downstream sensor. These sensors are heated to shorten the warm-up time the PCM actuates the heater circuit to provide correct voltage signal once the sensors are at operating temperature. Whenever it is being serviced, care must be taken since the sensors have permanently attached pigtails and electrical connectors that are very much vulnerable to damage, contamination, and mishandling. As for procedures of working with sensors, it is desirable to warm the engine when replacing the sensor because it makes it easy to remove, and the procedure includes the next steps: disconnect the electrical connector, unscrew the sensor with the help of a suitable sockets, apply anti-seize compound if the old sensor is used again, and check the tightness of the screws.