GMC 25143439 Catalytic Converter Assembly

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When the vehicle is raised for servicing underbody components, you should check the catalytic converter for leaks, corrosion, dents, and other damage. Additionally, check the flange bolts that attach the front and rear ends of the converter to the exhaust system. If damage is discovered, the catalytic converter should be replaced.

To check if a catalytic converter is restricted, you can use a vacuum gauge to diagnose the effect of a blocked exhaust on intake vacuum. Here are the steps: Connect a vacuum gauge to an intake manifold vacuum source. Warm the engine to operating temperature and place the transmission in Park with the parking brake applied. Note and record the vacuum reading at idle. Open the throttle until the engine speed reaches about 2000 rpm. Quickly release the throttle and record the vacuum reading. Perform this test three more times, recording the reading after each test. If the reading after the fourth test is more than one inch of mercury (in-Hg) lower than the idle reading, it may indicate a clogged or restricted catalytic converter, muffler, or exhaust pipes.