Cadillac 12597989 Sensor Assembly, Heated Oxygen (Position 2)

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The oxygen sensors, located in the exhaust system, monitor the oxygen content of the exhaust gas stream. There are three oxygen sensors. The two upstream sensors are located on the front and rear exhaust manifolds. The downstream sensor is located behind the catalytic converter. The oxygen content in the exhaust reacts with each oxygen sensor to produce a voltage output from 100 millivolts to 900 millivolts. The ECM monitors this voltage output to determine the ideal air/fuel mixture. The ECM alters the air/fuel mixture ratio by controlling the pulse width of fuel injectors. A mixture of 14.7 parts air to 1 part fuel is the ideal ratio for minimizing exhaust emissions, thus allowing the catalytic converter to operate at maximum efficiency. The oxygen sensor must be hot to operate properly. During the initial warm-up period, the ECM operates in open loop mode. The proper operation of the oxygen sensor depends on four conditions: Electrical, Outside air supply, Proper operating temperature, and Unleaded fuel. In addition to observing the above conditions, special care must be taken whenever the sensor is serviced. The oxygen sensor has a permanently attached pigtail and connector which should not be removed from the sensor. Grease, dirt and other contaminants should be kept away from the electrical connector and the louvered end of the sensor. Do not use cleaning solvents of any kind on the oxygen sensor. Do not drop or roughly handle the sensor. The silicone boot must be installed in the correct position to prevent the boot from being melted and to allow the sensor to operate properly. Disconnect the cable from the negative terminal of the battery. Some of the oxygen sensors are easier to remove and install from above, with the vehicle on the ground. Some are buried beneath hoses, cables and wiring harnesses, and are easier to remove from underneath the vehicle. Disconnect the oxygen sensor electrical connector. Note the position of the silicone boot, if equipped, and then, using an oxygen sensor socket, carefully unscrew the sensor from the exhaust manifold or exhaust pipe. Use anti-seize compound on the threads of the new or old oxygen sensor to facilitate future removal. Install the sensor and tighten it to the specific torque. Reconnect the electrical connector of the pigtail lead to the main engine wiring harness. Lower the vehicle and reconnect the cable to the negative terminal of the battery.