Decoding Noise and Vibration of Your Catalytic Converter

Miller CAT’s Guide to Addressing Rattling/Noise

When properly installed with the correct hardware, the user should not experience any significant noise or rattling. Our products have been designed to provide your car with optimal clearance to prevent your shield from coming into contact with your exhaust.

To properly address any noise you may hear, there are two conditions that must be met.

*If your shield required rivet nuts, make sure the rivet nuts were fully crushed and are not loose.

Miller CAT’s Guide to Troubleshooting Catalytic Converter

a picture of a Toyota Prius exhaust hangerIf you meet the two conditions above, please see the following suggestions.

Prius Gen 1/2 (2001-2009)

Replace exhaust hangers

Any vehicle that is older than 10 years should have their exhaust hangers replaced. Exhaust hangers keep your exhaust system from swaying too much. For Prius Gen 1/2 (2001-2009) owners, it is highly recommended that you replace the exhaust hangers. They are the cheapest and simplest solution to any rattling.

Prius Gen 3/C/V (2010-2019)

Verify all hardware was used

Ensure the shield was installed with the provided spacers and rubber dampeners.

Check the bends and recirculation hose clip

On the Gen 3 (non-Prius C/V), make sure all the 3D features (bends at the rear of the shield and bridges running along the recirculation hose) have been properly bent. There is also a clip on the hose that can be adjusted to prevent any contact with the shield.

Replace exhaust hangers

Replacing exhaust hangers can help ensure there is not excessive swaying of the exhaust system that could come into contact with the shield.

Prius Gen 4 (2016-2022)

Check the orientation of the shield

troubleshooting catalytic converterOur Gen 4 shield is symmetrical and users can incorrectly install the shield with the wrong side facing down towards the ground. A tip is that the M logo should always be on the right side of this shield when the owner is looking at it. The lip of the shield should also be facing toward the rear of the vehicle.

Honda Element

Check to see if the converter is an original converter

Any aftermarket converter is not guaranteed to fit properly due to the variance in the bends with aftermarket parts.

Replace exhaust hangers

New exhaust hangers will keep the exhaust system from excess movement.

If your vehicle still experiences vibration, please contact us at

DIY Guide on Fixing Your Catalytic Converter

If your catalytic converter is malfunctioning, this do-it-yourself (DIY) tutorial will help you figure out what’s wrong and fix it so that your car’s exhaust system works as efficiently as possible.

Diagnosis and Inspection

Start by doing a complete diagnosis of the issue. Look for loose or damaged parts in the catalytic converter, shield, and the complete exhaust system. Listen for strange noises, notice a decrease in performance, or notice an increase in emissions. The source of the problem can then be located with the help of this preliminary examination.

Essential Tools for DIY Converter Repair

It’s critical to have all the necessary equipment on hand before beginning the repair process. Stock up on tools like wrenches, sockets, pliers, jack stands, safety equipment like gloves and goggles, and a good torque wrench. If you have the proper equipment on hand, fixing the problem will go more quickly and easily.

Installation and Replacement of Your Catalytic Converter

If your evaluation concludes that a replacement is required, correctly put it in place by following these instructions:

Monitor and Follow Up

It’s important to keep an eye on your vehicle’s performance and exhaust system after a repair or replacement has been made. Keep an ear out for any sounds, vibrations, or rattles that persist after the installation process has been finished. Maintaining a properly functioning exhaust system and shield requires routine alignment checks.

Don’t be reluctant to contact Miller CAT’s devoted support team at for tailored assistance if your troubleshooting efforts don’t fix the problems and the car continues to vibrate. Careful installation and routine maintenance are essential for the quiet, trouble-free operation of your catalytic converter, which in turn improves your car’s performance and extends its life.