2008 Cadillac STS Oxygen Sensor

Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

The procedure is to turn the ignition off, remove the fuel injector sight shield, if necessary, disconnect the heated oxygen sensor (HO2S) electrical connector, remove the HO2S electrical connector from the wiring harness bracket, raise and support the vehicle, remove the HO2S from the catalytic converter.

You should not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor.

You should have a code clear with a scan tool, regardless of whether or not a DTC is set and HO2S heater resistance learn reset with a scan tool.

The recommended torque is 40 N.m (30 lb-ft).