Special caution has to be applied during the servicing of oxygen sensor as it incorporates a permanently installed pigtail and electrical connector, which if damaged or disconnected, will render the sensor useless. Grease, dirt and other contaminants should not get in contact with electrical connector and the louvered end of the sensor, and it is specifically directed that no cleaning solvents should be used on an oxygen sensor or air/fuel ratio sensor. These should not be dropped or handled roughly, also the silicone boot should be correctly fitted so not to melt and to function properly. Oxygen sensors are usually fitted in the exhaust manifold or
Catalytic Converter and it becomes very hard to unscrew when cold so getting the car engine running for few minutes is recommended before undertaking the job. First of all, loosen the nut on the negative cable and then safely lift the car on jack stands. The upstream oxygen sensor is mounted on top of the exhaust manifold, to reach this sensor, one has to trace the electrical lead to its connector to disconnect it. With an oxygen sensor socket, unscrew the sensor and with an 18 mm tap clean the threads of the sensor bore. Reinstall the old sensor, if this is done you must coat the threads with anti seize compound, for the new sensors this is not necessary as they are supplied with pre applied compound. Once the upstream sensor has been placed, be sure to retighten it to the recommend torque. The downstream oxygen sensor is installed at different locations depending on the emission package; Federal in the exhaust pipe after the catalytic converter, Low Emission Vehicles on the converter and Ultra Low Emission Vehicles between two converters. By now, the tester is disconnected from the downstream sensor; it is unscrewed using a special socket, and the threads of the sensor bore in the catalytic converter are cleaned. If the old sensor is to be reinstalled then put some anti-seize compound, but not in case of a new sensor. Last is the downstream oxygen sensor, which must be bolted to the factory torque when possible and installation is done in the reverse manner to its removal.