A catalytic converter is a mechanical device designed to convert the three most harmful elements present in a car’s exhaust into harmless elements. The three harmful elements are hydrocarbons (unburned gasoline), carbon monoxide (accumulated by gasoline combustion), and nitrogen oxides (formed when the nitrogen in the air is forced to combine with oxygen by the heat in the engine). A catalytic converter aids in converting carbon monoxide into carbon dioxide. It also helps in converting the hydrocarbons into water (H2O) and carbon dioxide. The nitrogen oxides are converted back into oxygen and nitrogen. A catalytic converter has no moving parts and is designed to last the normal operating life of the vehicle.

Most catalytic converters fail due to engine-related problems. Replacing the catalytic converter without diagnosing and repairing the cause of the failure may lead to another ruined converter. Typically, converter failures fall in one of the following categories: physical damage due to corrosion or from the converter coming into contact with a large object on the road surface.

Potential Causes:

• Overheated, melted, or broken converters
• Misfires – low compression, low spark, or no spark
• Engine mechanical, ignition, or control system failure
• Coated or oil-fouled substrate
• Excessive oil consumption (burning oil) – bad rings or valve seals
• Excessive carbon build-up in exhaust – incorrect timing of fuel mixture, faulty spark plugs or plug wires, faulty check valve, oxygen sensors
• Internal coolant leaks (head/intake gasket)
• Improper fuels or additives – E85, diesel, sulfur (found in some low-quality gasoline)
• Structural damage
• Physical damage such as dents or cracks from road debris, collision, speed bumps, etc.
• Metal fatigue or stress fractures
• Corrosion
• Contamination due to excessive oil consumption, internal coolant leak, or excessive carbon build up
• Melted substrate due to engine misfires which lead to excessive converter temperatures
• Thermal shock or cold-quenching – hot converter is suddenly cold quenched when driving through deep water or into deep snow
• Sudden drop in temperature forces the converter housing to contract, which can cause cracks or breakage of the ceramic substrate.
• Converter aging/lack of engine maintenance – cycles of damaging engine conditions will eventually deteriorate converter performance

Converters will get red hot when excess fuel is introduced directly into it, along with sufficient oxygen to burn the fuel. This is not a problem with the converter itself, but the result of a problem with the fuel system or ignition that allows unburned fuel to pass through the engine and then travel down into the converter. If the root cause is not corrected, the new converter will melt as well. Common causes of a melted converter are:

1. A three-way plus air vehicle running rich, and when the air is injected into the converter, the rear brick will melt as the excessive fuel now has enough oxygen to burn inside the converter
2. Vehicle is running rich with an exhaust leak, and when the air is drawn into the exhaust pipe and is combined with the excess fuel, it will burn in the converter
3. The vehicle has a misfire. When the air-fuel charge leaves the combustion chamber without firing, it will travel through the exhaust pipe and burn in the converter.

If a converter is operating too long at a high temperature, the substrate may “melt down” and turn into a solid mass inside the converter. The vehicle may seem sluggish, as if there was a loss of power. Other causes might be:

1. Upstream converter has broken up and the debris has clogged a downstream unit
2. The support mat may have become damaged and no longer retaining the brick in the correct position, allowing the brick to shift and block the exhaust flow.

If a replacement converter fails after a short period of time, then the root cause of the original failure has not been addressed. Some causes are contamination by silicone-based sealants, coolant leaks, oil blow by, high sulfur fuel, and/or rich fuel mixtures forming carbon deposits can quickly coat the substrate preventing it from working effectively.

Likely not, as converter meltdown is primarily contributed to an engine misfire. The unused air and fuel resulting from an engine misfire will cause an intense fire inside the catalytic converter, damaging it internally. Normal operating temperatures of a converter are 500-800°F, and up to 1200°F when the vehicle is under heavy load. To melt the catalytic converter’s substrate, the temperature inside the converter would have to exceed 2000°F.

A P0420 low efficiency code does not always indicate that the converter needs to be replaced. On newer vehicles, a low efficiency code can occur if the exhaust feed gases are not of proper balance to allow the converter to operate efficiently. An experienced emissions technician may be able to identify and resolve this concern with a scan too. The most effective way for most technicians to diagnose this condition is through the use of a 5 gas analyzer, performing the switch-ratio scan tool test, and Oxygen Storage Capacity (OSC) scan tool test.

It is illegal to install a catalytic converter based solely on physical shape, size, configuration, or pipe diameter.

Proper Steps

• Determine Vehicle Manufacturer
• Determine Vehicle Model
• Determine Vehicle Year
• Determine Vehicle Specific Engine Size
• Vehicle Test Group / Engine Family Number
• Visit carbcats.com or the California Air Resources Board Aftermarket Converter Database to see which aftermarket part is approved to install.
• If no EXACT match is found, then there are no aftermarket catalytic converters available at this time.

When installing a universal converter, it must still meet the emission requirements of the vehicle and cannot be chosen by size alone. By looking up your specific vehicle in the catalog or web site, you will find the recommended universal converter with the appropriate loading. If a universal converter is not listed for your specific application, a direct fit must be used; if a direct fit is not listed, the only alternative is the Original Equipment Manufacturer (OEM) part.

No. A diesel engine has different emission requirements and a gas engine converter will not function on a diesel engine.

The best way to determine this is to look at the vehicle’s emissions system label. The label can usually be found on either the front radiator support, the strut tower plate, or under the engine hood. If the vehicle is California Emissions Certified, the label will reference “CARB,” “California,” or “ARB.” Once the emissions certification has been found, the “Engine Family Number,” or sometimes referred as “Test Group Name,” “Engine Family Code,” or “Group Number” must be determined. This number can be found on the Emissions Control Information Label.

Every CARB-compliant replacement converter must display a certification stamp or label on the converter shell that includes:

• CARB Executive Order approval number
• Manufacturer Part Number
• Date of Manufacture
• Exhaust Flow Direction

Engine changes present a problem and challenge to car owners and technicians. Contact your local Bureau of Automotive Repair (BAR) to make sure your vehicle is compliant to the standards.

Yes, if it has been tested for this type catalyst by the manufacturer in compliance with CARB aftermarket converter procedures.

There is no guarantee that replacing the converter will keep a fault code from coming back. If engine performance issues exist, and it has not been repaired, the P0420/P0430 fault code may reoccur.

1. Complete a warranty card in triplicate with the original going to the customer, one copy to the installer, and one copy to the manufacturer of the converter.
2. Retain a copy of the warranty card for a minimum of four years from the date of the installation.

Yes, since converters are designed to last the life of the vehicle, the technician should identify and correct the root cause of the original converter failure.

Checklist:

• Make sure any other codes are corrected prior to installing the new converter. This is especially true for misfire, mass air flow, rich/lean conditions, and O2 response rate codes.
• Pressure check the cooling system to test for leaks which could contaminate the new converter.
• Repair any exhaust leak that may be present. A stethoscope or a smoke test are successful ways in detecting an exhaust leak. However, a smoke test can not only find escaping exhaust, but also air that is being sucked in. An exhaust leak may affect converter and O2 sensor operation.
• Check O2 operation - The front sensor should have good frequency, amplitude, and response rate and average 450mv. The rear should be fairly steady at idle and above 450mv (typically 650-850mv).
• If both of the above O2 sensor readings are not present, the vehicle should be checked with a 4 or 5 gas analyzer and repairs should be performed.

With more and more catalytic converter theft, converter theft prevention and shield awareness is growing and people want to know how effective these anti-theft devices are before investing in one for their own vehicle. This is understandable since depending on the make and model of the vehicle, catalytic converter shield costs can be pricey. However, when considering the cost of replacing a catalytic converter and the effectiveness of catalytic converter shields, a shield is a worthwhile investment. In short, catalytic converter shields work and protect your vehicle. High-quality converter protection devices like Cat Shield™ by Miller CAT make it difficult for thieves to cut through. The added time and effort it takes to tamper with the 304 stainless steel shield can deter would-be thieves from targeting your vehicle in the first place.

Any vehicle is at risk for catalytic converter theft, but some models are more targeted than others. According to Carfax, location matters and the most targeted vehicles can vary from coast to coast. Those who live in the western states see many catalytic converter thefts with the Toyota Prius, Subarus, Ford F-Series and Econoline. In the eastern portion of the US, we also see Subarus, Toyotas, and Ford vehicles. In the south, we see an uptick in theft in sedans such as the Chevrolet Cruze and Dodge Avenger. And making the top 10 in the midwest, we see a high rate of catalytic converter theft in the Chrysler 200 and Jeep Patriot. Nationwide, there is no pattern of a single body style or manufacturer. However, hybrid cars, luxury cars, and trucks top the lists because of the value of the precious metals their converters contain, such as rhodium, palladium, and platinum.

If you are a victim of converter theft, the first thought is often, "How much is it to replace a catalytic converter?" Catalytic converter replacement costs can vary based on the quality of the replacement part, make and model of the vehicle, labor cost, and any other additional diagnostic or parts/repair fees. Most full or comprehensive car insurance plans cover replacement; however, those with liability-only coverage will pay out of pocket. Depending on your location and vehicle model, catalytic replacement costs can run you anywhere from $1,000-$3,000.

A catalytic converter shield is a protective barrier between the converter and thieves and can help prevent catalytic converter theft. The best catalytic converter shields offer the ultimate security with the highest quality materials, such as stainless steel and advanced engineering and design technologies supplying optimum protection.

Even when taking precautions and installing anti-theft catalytic converter shields, the unfortunate can happen. Given enough time and the right tools, thieves can cut through a low quality catalytic converter shield. If attempting to cut through Miller CAT’s Cat Shield™, the amount of noise and time would make thieves reconsider because of the intricate design and superior materials of a Miller CAT Cat Shield™. Not even a Milwaukee Super Sawzall nor a Diablo carbide tip blade can withstand our 304 stainless steel shield.

Many people ask why their Prius converters are being stolen in record numbers. Why do people target a hybrid versus a large truck? Aren’t Priuses suppose to be clean vehicles? The answer is palladium and rhodium. It is true that Priuses are CVs and are classified at the Super Ultra-Low Emissions Vehicle (SULEV) level, but in order to obtain that classification, Toyota had to ensure the Prius passed a strict emissions test. The reason hybrids have some of the highest precious metal content out of any vehicle is because hybrids turn on and off their gasoline engines frequently to save gas. However, most of the harmful emissions are produced during the initial start of the engine called a cold start. A catalytic converter needs to reach an optimal temperature to efficiently convert harmful gases, but frequent cold starts constantly lower that temperature and make the converter inefficient at reducing harmful emissions.

In order to solve this problem, Toyota overloaded their hybrid converters with palladium and rhodium. 10-15 years ago (2004-2010), palladium was only around $200-$300 per troy ounce and rhodium averaged around $3,000. Today, palladium is around $2,600 and rhodium is around $27,000. At the time Toyota designed their converters, the price of metals was cheap, but due to global supply constraints and the rising need for cleaner cars, the prices of those metals jumped upwards of 700% for palladium and 300% for rhodium in the past few years.

Due to these factors, thieves are making the most money off of Prius converters and making life difficult for Prius owners. We highly recommend our Cat Shield™ to prevent such theft and to protect your investment. Let us know if you have any questions that aren’t answered here.

We’ve done extensive testing on the front and rear converters with and without the Cat Shield under numerous driving conditions. Our data reveals that during city or freeway driving, there are minimum temperature increases (10 degrees max) and there actually lower temperatures with the Cat Shield at the rear position when driving on the freeway. This is likely due to the Cat Shield making the vehicle more aerodynamic, reducing turbulence, and making the louvers more effective at drawing out heat.

Even right after turning the vehicle off after aggressive driving, the Cat Shield will be safe to touch (although we recommend using proper safety equipment at all times when handling the shield). Temperatures at different points of the shield on average were 80 degrees. We also measured temperatures on the underbody of the car near the hottest points (front and rear converters) and saw consistent and similar temperatures of 80-200 degrees.

Based on the temperature data, we conclude that the shield will have no impact on increased cabin temperature, will not pose increased danger to flammable material underneath the car (in fact, the shield protects material from touching the hottest part of the exhaust, the converter(s)), or prematurely wear down exhaust components.

Some competing products will use rivets or say their hardware is corrosion-resistant, but when differing corrosion-resistant metals come into contact, they will corrode by a process called galvanic corrosion (also called bimetallic corrosion). Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. Basically, it is when two different metals come into contact with each other and cause premature rust and corrosion.

We use stainless steel hardware and zinc coated rivet nuts to prevent rust and corrosion.

The underneath steel frames of the Prius are coated and do not come into direct contact with the aluminum shield. Even after drilling holes into the frame, the zinc-coated rivet nuts are the only pieces that touch any uncoated steel and the zinc acts a protective barrier between the metals. We take every piece of hardware into consideration to make sure none of our parts will cause premature rust or corrosion. Be wary of products that do not use stainless steel or zinc-coated materials (such as rivets, self-tapping nuts or screws) because they will likely lead to galvanic rust.

All our Cat Shields are designed with louver vents to give our customers the best product on the market. They help cool your vehicle and protect it from debris.

Rivet nuts are great pieces of hardware that allow one to get threaded holes where there initially weren't any. Understanding the need to replace O2 sensors and doing other maintenance to the vehicle, we designed our shield for rivet nuts. This way, you can remove the shield when needed without doing any damage to the shield or vehicle. Our tamper-proof screws coupled with the rivet nuts provide the best combination of protection and convenience.

There are many dealers who are selling Cat Shield by Miller CAT and installing them on customer vehicles. While we cannot guarantee an issue could arise, nothing on the exhaust system should be voided because of the shield. If there is ever any doubt, our shields are removable, which should ease any concern you might have.

We thoroughly test and develop our products with you in mind. You cannot place a sheet of metal underneath the car and expect to have zero noise and vibrations. In our design, we’ve considered almost every variable such as the movement of the converter, exhaust system, engine, and angles and planes of mounting points. We use spacers and noise dampeners to ensure that the only time you know the shield is on is if you look below the vehicle. The Prius Liftback, Prius C, and Prius V specifically use spacers and dampeners.

We use 5052 premium grade aluminum, which was chosen because of its strength and its excellent resistance to saltwater. For those customers who live near the ocean or in areas where roads are heavily salted, our shields are great for you!

There is no perfect prevention against catalytic converter theft. With the right tools, time, and willingness, an experienced thief can remove any anti-theft protection device.

However, our goal is to deter the thief as much as possible so that they will move on from your vehicle. We have proven evidence of deterrence from our customers that show thieves see the shield and move on. If someone tries to cut off the shield, they will create a lot of noise and it will take a long time to get the shield off. If a thief is looking to spend just a few minutes to steal a converter, they will think twice when they realize the job will require different tools, more time, and more noise. We’ve tested our stainless steel shields against a Sawzall, which was not pretty and definitely loud and time-consuming.