When servicing the oxygen sensor, remember to keep the electrical connector clean and not solder the sensor's wiring harness, because the sensor needs an outside oxygen source, delivered through its wiring harness. The 1/1, 1/2, 1/3, 2/1 and 2/2 sensors are called oxygen sensors, with the pre-catalyst ones in front of the mini-cats and the post-catalyst ones placed after the mini-cats on both ends of the converter. First, wait for the exhaust system components to cool, prepare and raise the vehicle. Unplug the connector between the O2S sensor and the aerator, being careful not to pull on the wire when you do it. You should use a special tool to take out and insert the O2S sensor. No need to coat the threads on the new oxygen sensors with anti-seize compound, because they have been coated at the factory. Attach the O2S sensor, secure it to 30 Nm (22 ft. lbs.) torque and plug in the connector. After that, lower the vehicle.