GMC 20953446 3Way Catalytic Convertor Assembly (W/ Exhaust Manifold P

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Because of a Federally-mandated extended warranty, it is recommended to check with a dealer service department before replacing the catalytic converter at your own expense. A catalytic converter is an emission control device in the exhaust system that reduces certain pollutants in the exhaust gas stream. There are two types of converters: an oxidation catalyst that reduces hydrocarbons and carbon monoxide, and a reduction catalyst that reduces oxides of nitrogen. If you suspect that the converter is malfunctioning, take it to a dealer or authorized emission inspection facility for diagnosis and repair. When raising the vehicle to service underbody components, inspect the converter for leaks, corrosion, dents, and other damage. Check the welds and flange bolts and nuts that attach the front and rear ends of the converter to the exhaust system, and replace the converter if any damage is noted. Catalytic converters can become clogged or plugged up, and a vacuum gauge can be used to diagnose the effect of a blocked exhaust on intake vacuum. If the fourth reading is more than one in-Hg lower than the reading at idle, the exhaust system might be restricted. To replace the catalytic converter, raise the vehicle and secure it on jackstands. Spray penetrant onto the threads of the exhaust manifold-to-catalyst pipe nuts and bolts, as well as the catalyst pipe-to-exhaust pipe nuts and bolts. Disconnect and remove the upstream and downstream oxygen sensors. Unscrew the exhaust manifold-to-catalyst pipe flange nuts and bolts, and unscrew the clamp that secures the slip joint between the exhaust pipe behind the catalytic converter and the pipe ahead of the muffler. Remove the catalytic converter assembly and discard the old flange gasket. Installation is the reverse of removal, using new flange gaskets, bolts, and a new clamp.