Hummer 12615194 Sensor Assembly, Heated Oxygen (Position 3)(Post, Cat)

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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 crucial for the feedback loop between the oxygen sensor and the Powertrain Control Module (PCM) to maintain the perfect air/fuel ratio of 14.7:1 that the catalyst needs for optimal operation. All vehicles covered have On-Board Diagnostics II (OBD-11) engine management systems, which means they have the ability to monitor the performance of the catalytic converter. All models covered by this manual have four heated oxygen sensors: one upstream sensor per cylinder bank and one downstream sensor per cylinder bank. Special care must be taken whenever a sensor is serviced, as they are extremely delicate and cannot be dropped or handled roughly. The upstream and downstream oxygen sensors are heated to speed up the warm-up time during which the sensors are unable to produce an accurate voltage signal. The circuit for each oxygen sensor heater is controlled by the PCM. To remove the upstream or downstream oxygen sensor, the vehicle must be raised and securely placed on jackstands. The sensor electrical lead must be traced to the connector and disconnected before unscrewing the sensor with an oxygen sensor socket. If the sensor is difficult to loosen, penetrating oil can be sprayed onto the sensor threads and allowed to soak in for a while. When installing the old sensor, anti-seize compound should be applied to the threads to facilitate future removal. If installing a new oxygen sensor, it's not necessary to apply anti-seize compound to the threads as they already have anti-seize compounds on them. The installation process is the reverse of removal, and the sensor must be tightened to the torque specifications.

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 crucial for the feedback loop between the oxygen sensor and the Powertrain Control Module (PCM) to maintain the perfect air/fuel ratio of 14.7:1 that the catalyst needs for optimal operation.

All models covered by this manual have four heated oxygen sensors: one upstream sensor per cylinder bank and one downstream sensor per cylinder bank. The sensors are heated to speed up the warm-up time during which the sensors are unable to produce an accurate voltage signal.

When installing the old sensor, anti-seize compound should be applied to the threads to facilitate future removal. However, if installing a new oxygen sensor, it's not necessary to apply anti-seize compound to the threads as they already have anti-seize compounds on them.