GM 12580466 Sensor Assembly, Heated Oxygen (Position 1)

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An oxygen sensor is a galvanic battery that produces a small voltage output in response to the amount of oxygen in the exhaust gases. This voltage signal is the input side of the feedback loop between the oxygen sensor and the Powertrain Control Module (PCM). Without it, the PCM would be unable to correct the injector on-time to maintain the perfect air/fuel ratio of 14.7:1 that the catalyst needs for optimal operation. All vehicles have On-Board Diagnostics II (OBD-11) engine management systems, which use an oxygen sensor ahead of the catalytic converter and another oxygen sensor behind the catalytic converter to verify the accuracy of the feedback loop. The models have two heated oxygen sensors: one upstream sensor located on the rear exhaust manifold and a downstream sensor located under the vehicle, behind the catalytic converter. Both sensors are heated to speed up warm-up time. When servicing a sensor, special care must be taken to avoid damaging the pigtail or electrical connector, keeping contaminants away, and not using cleaning solvents. Oxygen sensors are delicate and should not be dropped or handled roughly. The silicone boot on the sensor must be installed correctly to prevent melting. When replacing the upstream oxygen sensor, the ignition coil assembly may need to be removed for better access. The sensor can be unscrewed using an oxygen sensor socket, and if reusing the old sensor, anti-seize compound should be applied to the threads. The installation process is the reverse of removal. For the downstream oxygen sensor, the vehicle must be raised and securely placed on jackstands. The sensor can be located and disconnected, then unscrewed using an oxygen sensor socket. Again, if reusing the old sensor, anti-seize compound should be applied to the threads. The installation process is the reverse of removal.

The purpose of the oxygen sensor is to provide a voltage signal as input to the feedback loop between the oxygen sensor and the Powertrain Control Module (PCM), allowing the PCM to correct the injector on-time and maintain the optimal air/fuel ratio for the catalyst's operation.