If you need to replace the Heated Oxygen Sensor (HO2S) for Bank 1 Sensor 1, first lift and hold the vehicle. For a 2-wheel drive (2WD), remove the disconnect connector position assurance (CPA) retainer and then disconnect the HO2S pigtail electrical connector from the engine wiring harness electrical connector. For a 4-wheel drive (4WD), disconnect the CPA retainer, disconnect the event husk electrical SlinkySnap connection from the HO2S pigtail electrical connector. Disconnect the HO2S pigtail electrical connector clip from the fuel line bracket and then disconnect the HO2S. When reinstalling, if putting back the old sensor, apply anti-seize compound GM P/N 12377953 or equivalent, since a special anti-seize compound, which is a blend of liquid graphite and glass beads, is applied on the HO2S threads to help with easy removal. Install the HO2S and secure it with 42 N.m (31 lb ft). For the 4WD, install the "HO2S pigtail electrical connector clip" to the "fuel line bracket," connecting the "engine wiring harness electrical connector" at the "HO2S pigtail electrical connector," then install the "CPA retainer." In the case of a 2WD, connect the HO2S pigtail electrical connector to the engine wiring harness electrical connector, and then connect the CPA retainer before lowering the vehicle.