Step 1: Set the parking brake and block the back tires. Using the floor jack, lift the vehicle at the same locations on each side for stability. Secure each point on jack stands. Raise it high enough so you can move around and work.
Step 2: Locate the catalytic converter underneath your vehicle. It’s usually located near the front of the vehicle behind the exhaust manifold. If your vehicle has more than one converter (common on cars with V6 and V8 engines), note the faulty bank that was listed on the OBDII Scanner.
Step 3: Remove oxygen sensors mounted to or near the converter. If there are no sensors to remove, which is rare on cars newer than the mid-90s, move on to step 4.
Step 4: Spray penetrating oil generously on the exhaust flange hardware and flanges. Let them soak for a few minutes. These nuts and bolts are prone to seizing due to dust, debris, rust, and high temperatures. They are exposed to the weather and road chemicals. Expect them to give you a hard time. You may need to spray them more than once and take a break.
Step 5: Check your nuts and bolts for sizes and get the right wrench or socket that fits tight. You do not want a wrench or socket that is loose or has wiggle room. You will round the head of the bolt and create new words when your knuckles hit the car’s undercarriage. We just went back up and added mechanic’s gloves to the tool list after writing that.
The socket extensions and extensions with flex joints may come in handy here. Use them if you find some nuts and bolts that are hard to reach with standard sockets or wrenches.
Once the hardware is removed the converter should come free. It may take a little twist and pull to loosen it up. If you need to, the penetrating oil could help here, as well.
Step 6: Place the new catalytic converter and place new flanges and gaskets to prevent any exhaust leaks.
*DIY Mechanic’s Note*: Make sure the new catalytic converter is the correct one for your vehicle and your engine’s output. Emissions tests and the coinciding regulations may vary from state to state and county to county. Having the incorrect converter may cause you to fail your emissions test.
Step 7: Install your new and proper catalytic converter by using steps 1-5 in reverse order
*DIY Mechanic’s Note*: When you replace your converter, replace O2 sensors near the converter, too. Save time on future repair costs.