Because of the Federally mandated extended warranty covering emissions-related components such as the catalytic converter, it is advisable to check with a dealer service department before replacing the converter at your own expense. The catalytic converter is an emission control device in the exhaust system that reduces pollutants from the exhaust gas stream. There are two types: the oxidation catalyst, which reduces hydrocarbon and carbon monoxide levels by adding oxygen, and the reduction catalyst, which lowers oxides of nitrogen by removing oxygen. These catalysts are combined into a three-way catalyst that addresses all three pollutants. Testing a catalytic converter can be costly, so if malfunction is suspected, it is best to take the vehicle to a dealer or authorized emissions inspection facility for diagnosis and repair. When servicing underbody components, inspect the converter for leaks, corrosion, dents, and other damage, including the welds and flange bolts. Although catalytic converters rarely break, they can become plugged; a vacuum gauge can help diagnose a blocked exhaust. To check for a restricted converter, connect a vacuum gauge to an intake manifold vacuum source, warm the engine, and record vacuum readings at idle and after quickly opening the throttle. If the reading after the fourth test is more than one in-Hg lower than the idle reading, the exhaust system may be restricted. For replacement, securely raise the vehicle on jackstands, remove the downstream
Oxygen Sensor, and spray the nuts on the exhaust flange studs with penetrant before removal. Loosen the clamp behind the catalytic converter, detach the nuts connecting the catalyst to the exhaust manifold, and separate the converter from the exhaust system. Before installing the new converter, coat the threads of the exhaust manifold studs and the clamp bolt with anti-seize compound, ensuring all fasteners are tightened securely. Installation follows the reverse order of removal.