The 2002 Chevy Avalanche has two catalytic converters. The catalytic converters are located in what most mechanics refer to as the y-pipe. The catalytic converter is part of the exhaust system and is always in front of the muffler. The inside of the catalytic converter is constructed like a honeycomb -- passages and small ceramic beads coated with catalysts make pollutants less harmful. If the catalytic converter fails, it will not allow the exhaust gases to flow and the car will not run. You must replaced a damaged catalytic converter.
Take the negative (-) cable off the battery with a wrench. Use the jack to jack up the truck. Place the vehicle on on jack stands.
Disconnect the y-pipe at the exhaust manifolds by removing the mounting nuts on both right and left exhaust manifolds. Use a socket and ratchet with a long extension for this task.
Unplug the electrical plugs on the right and left oxygen sensors. The oxygen sensors are located in the y-pipe, which is in front of the catalytic converters. Use a socket and ratchet to take off the two bolts and nuts connecting the y-pipe to the exhaust pipe. Take the gaskets out and remove the y-pipe with the catalytic converters in it from the vehicle. Remove both oxygen sensors from the old y-pipe.
Put both oxygen sensors into the new y-pipe with a socket specially made for oxygen sensors. Take a wire brush and clean the exhaust manifold where the gasket seats to the manifolds. Put the y-pipe up to the exhaust manifolds with the inner nut on each side. Hold the y-pipe up and place the gasket between the y-pipe and the exhaust pipe; replace both nuts and bolts making sure the bolts go through the gasket.
Place the two gaskets in the pipe that attaches to the exhaust manifolds and replace the other two nuts. Make sure the gaskets are seated straight on both exhaust manifolds and tighten all four nuts.
Jack up the vehicle, remove jack stands and lower the vehicle. Clean the battery post and connect the negative cable to the battery.
