The emission control device of the exhaust system that minimizes some pollutants (hydrocarbons, carbon monoxide and oxides of nitrogen respectively) is called a catalytic converter, and there are two types of catalytic converters namely; oxidation catalyst and reduction catalyst. All three pollutants can be reduced in a so-called Three-Way Catalyst. Two catalysts are fitted to V6 models, one beneath the exhaust manifold flange and another fitted beneath the exhaust manifold; four-cylinder models usually have a single catalyst either near the rear end or directly below the exhaust manifold, and subsequent models have the catalyst built into the exhaust manifold. Should there be an indication of a problem, it is prudent to drop over at a dealer or official emission inspection center to have it diagnosed, because the equipment to perform the test is very costly. It should be checked frequently in terms of leaks, corrosion, and other damage, in case any problem has been identified, converter has to be replaced. A vacuum gauge can be used to monitor intake vacuum at idle and at throttle openings to check the presence of a clogged converter: a big fall in vacuum rate can indicate a restriction. In order to replace it, the vehicle must be lifted up, and replacement oil used which flows through fasteners at the exhaust manifold flange and catalyst flanges. Once the
Oxygen Sensor electrical connector has been detached, and the oxygen sensors have been taken out, it is possible to remove the catalytic converter assembly. Only new flange gaskets must be installed, and all fasteners placed with a firm tight fit using anti-seize compound on the threads.