GM 12578624 Sensor,Heated Oxygen(Position 2)

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Two oxygen sensors are equipped by every model, the pre-converter oxygen sensor and the post-converter oxygen sensor. The voltage output of the pre-converter oxygen sensor is affected by a variety of factors, including the amount of remaining oxygen in exhaust gases after combustion. The PCM constantly monitors this signal to determine fuel injector pulse width requirements and maintain a 14.7:1 air/fuel ratio. On the other hand, post-catalyst O2 sensors do not affect mixture control but their signals are used by the PCM to monitor catalyst efficiency. To work properly they require correctly wired electric circuits, ventilation, operating temperature and lead-free petrol. If any sensor problem is detected by PCM it uses diagnostic trouble codes to set open-loop fuel control mode. When replacing an O2 sensor one should be careful not to damage it or its electrical connector. The post converter one might necessitate raising the vehicle while pre-catalyst can be changed without raising it up. A ratchet wrench or socket that fits must be used to remove the sensored spark plug as well as coating threads with anti-seize compound before installation is done; after which connecting electrical connector is necessary before lowering down vehicle all these are completed successfully.

The electrical connector should be reconnected and the vehicle should be lowered.

No, the post-converter oxygen sensor has no effect on PCM control of the air/fuel ratio.