When your “check engine” light is on with catalyst efficiency codes, or your vehicle fails an emissions inspection for excessive tailpipe emissions, sometimes the catalytic converter must be replaced. This component is placed in the exhaust stream after the engine, but before the muffler.

A catalyst is a material which will cause a chemical reaction without being consumed in the reaction. This is critical, because the materials used for the reaction are incredibly expensive, precious metals. The most common of these metals are Platinum, Palladium, Rhodium and Cerium. Feel free to look at their current market value to get an idea of their cost, and then use this information to consider the price of quality catalytic converters.

A catalytic converter consists of a metal shell that reduces down to the size of the exhaust pipe on your vehicle, both at the front and rear. Inside the metal shell there is typically a monolith of ceramic material. Ceramics are typically used for their heat resistance, low thermal expansion, and porosity. Essentially, it looks like a long, very small holed honeycomb. This shape and material creates a large surface area to afford the most possible contact with the exhaust gases to catalyst metals. The way that the catalyst materials are applied to the honeycomb is suspended in a slurry called a washcoat. This is a process that is much more than simply dipping the monolith into a bath with the metals suspended in the slurry. It is a highly engineered process done with precise control that even allows for changing distribution of the catalyst metals within the monolith. Additionally, there are different mixtures of washcoats applied to the monolith. The first section is typically coated with Rhodium for oxides of nitrogen reduction into nitrogen and oxygen. The next is a cerium layer to promote oxygen storage. This oxygen is then used in the final section of the catalyst where hydrocarbons and carbon monoxide (partially or unburned fuel), is mixed with a platinum/palladium or platinum/rhodium mixture to change carbon monoxide and hydrocarbons into carbon dioxide and water. No engine is capable of producing perfect combustion, and due to environmental concerns, the catalytic converter is used to reduce the pollution a great deal further to meet stringent standards for pollution control.
Now that we have learned a little bit about what is in a catalytic converter, let us think about the cost of both discount and quality converters. It is possible to call a discount retailer and purchase a catalytic converter for your vehicle for a price close to $100. However, the converter from the manufacturer of your vehicle will probably be somewhere in the range of $600 – $2,500. You may even hear from the discount supplier that the converter they sell is federally certified or EPA certified, but this doesn’t necessarily mean anything. The only converters that you can be assured will pass the stringent state of Colorado I/M 240 test is either an original equipment converter from the manufacturer, or one that is certified by the California Air Resources Board.

CARB certified converters are manufactured, tested and certified to much higher standards than the ones that claim federal or EPA certification. There is greater oversight and there must be a specific CARB code printed onto the converter. With these converters, we can be sure that it will pass the I/M 240 test, and hopefully the algorithm required by the fuel management system of your vehicle to successfully pass the catalyst efficiency monitor tests.

We have tried the discount catalytic converters on vehicles that have failed the I/M 240, and after installation they may do well oxidizing CO and HC, but have little to no effect on NOX. This is due to the fact that the discount converters do not typically have a NOX reduction catalyst. This is especially problematic because the tightest requirements of the I/M 240 is for NOX reduction. Oxides of nitrogen combine with sunlight to cause photochemical smog. This is a major respiratory aggravator as well as the cause of the brown cloud or haze in large cities. The state of Colorado considers NOX reduction to be the most important part of the emissions testing program. As a matter of opinion, I will say with nearly 100% certainty that if a federal or EPA certified converter is installed on your vehicle to help correct a failed tail pipe emissions test, it will fail for a spectacular lack of NOX reduction, although it may be acceptable for CO and HC oxidation. I have never installed a discount converter that would pass the I/M 240 test.

The simple fact of the matter is catalytic converters are priced according to the commodity market value of the precious metals used as catalysts, as well as the highly engineered process for creating the best possible layout of the catalytic converter interior to maximize pollution reduction. There is simply no way to make a catalytic converter cheaper without some kind of short cut. Not a great deal can be done to lower the price of catalytic converters with volume manufacturing or increased production efficiency. It really comes down to commodity pricing of rare, expensive, precious metals. It is fairly expensive to use enough of these metals in your catalytic converter to effectively reduce emissions, and this is the main controller of cost.

I hope I have given you enough information to understand the cost of these components and the reason that buying the right quality converter is so important

Marc DuBois
Master Automotive Technician
Advanced Auto Pros Inc