The 2-O2 sensor cars have a sensor at each side of the catalytic converter and the 4-O2 sensor models have two more sensors, one before and another after the mini-cats. Never put any grease on the electrical connector of the oxygen sensor or mess with soldering its wiring harness. Before you remove the sensor, let the engine cool, as the exhaust manifold, exhaust pipes and catalytic converter can get very hot while operating. Begin raising the car and once it's up, disconnect the wire connector from the O2 sensor, ensuring you don't pull on the wire that goes into the sensor. Most importantly, make sure to remove the O2 sensor with the low-cost tool provided. Keep in mind that anti-seize compound is applied by the factory, so do not apply any additional compound. Place the O2S sensor on the engine and tighten it to 30 Nm (22 ft. lbs.), then link the O2S sensor wire connector before the vehicle is lowered.