The catalytic converter in your car’s exhaust system has a complex emissions-related job to perform. Placed between the engine and the muffler, it reduces the amounts of the three primary pollutants found in the exhaust gases of internal combustion engines: nitrogen oxides, carbon monoxide, and hydrocarbons. By passing the engine’s exhaust through the catalytic converter’s honeycomb-like ceramic structure, which is coated with precious metals like palladium, platinum, and rhodium, these three pollutants are converted into less harmful substances. Catalytic converters have been mandated since 1975, with nearly every car required to have one. 

Another major part of your car’s catalytic converter system is the oxygen sensor, which interfaces with your engine’s electronic control system to monitor its exhaust gas flow, preventing it from running either too rich or too lean. This keeps your emissions within the legal limits, while also balancing  your car’s power and economy. 

Catalytic converters can be susceptible to some common problems over their lifespan, which should normally be the vehicle’s entire life. Let’s look at these problems individually, going over why they may happen and what the best ways are to fix them.

Your catalytic converter hangs underneath your car with the rest of the exhaust system, so anything that can cause damage to your muffler or exhaust pipes can also “impact” your catalytic converter. That can mean debris on the road, as well as going over a curb while driving. Doing this type of damage to your catalytic converter can cause its ceramic internal structure to crack or break, affecting its ability to properly convert the toxic substances in your unfiltered exhaust gases.

Physical damage anything like what’s shown above is likely to require replacing your catalytic converter. This type of damage to your catalytic converter will probably also lead to the illumination of your Check Engine Light, since your emission control system will severely impacted by it.

Be aware that certain states require CARB-compliant catalytic converter replacements, which meet the stricter standards set out by the California Air Resources Board. These standards apply to all cars replacing their catalytic converters in California, New York, and Colorado, including out-of-state vehicles. In addition, all CARB-compliant cars replacing their catalytic converters in the state of Maine that were made during or since the 2001 model year must be fitted with a CARB-compliant replacement unit. Be sure to check the local regulations in the state where you reside before replacing your car’s catalytic converter, and don’t even think about whether you should drive without a catalytic converter. 

There are numerous ways that your car’s catalytic converter can become clogged, and none of them have anything to do with the issue of external physical damage. If you have a leak of coolant or oil that makes its way into the exhaust system or into the cylinders, it can clog up the fine ceramic structure coated with those precious metals inside the convertor, rendering it ineffective. Clogging can also be the result of using substandard fuel, misfiring spark plugs, a fuel-air mix that’s too rich, or just wear and tear over time. 

If you are facing the possibility of a clog, there are ways to clean your vehicle’s catalytic converter at home. It’s definitely worth a try if the only other alternative is replacing it out of pocket.

The symptoms of a clogged catalytic converter are pretty tough to ignore. You may experience much worse fuel economy as you drive, hard starting, high heat levels that can start fires under your car, a noticeable lack of performance from your engine, a rotten egg-like smell, and all of this will likely also trigger the Check Engine light on your dashboard to go on. Keep in mind that the clogged catalytic converter is creating an obstruction in your engine’s exhaust system that your engine has to work against, which can lead to leaking oil, seals blowing out in the engine, or even a blown engine if you wait too long to fix the problem. 

This unfortunate scenario has been happening to car owners across the country. California’s the leader in catalytic converter thefts nationwide, with New York, Illinois, Texas, and Florida rounding out the top five. A thief can cut off your catalytic converter in about a minute, making it unlikely they’ll be apprehended unless they are caught sawing it off. And while thieves get $50 to $500 for stolen converters, you’ll have to pay up to $4,000 to repair your car. While SUVs and pickup trucks, with their increased ground clearance, make the easiest targets, we have compiled a list of the cars most likely to have their catalytic converters stolen.

There are some ways to minimize the risk of having your car’s catalytic converter stolen. These include parking your car in a closed garage, the use of motion sensor lighting where you park your car, never failing to set your car’s alarm and locking your vehicle. If you must park in an area out in the open, be sure that it is at least lit very well.

Additional strategies for protecting your catalytic converter from theft involve making it tougher to remove or making it identifiable. Theft prevention devices include straps, clamps, or cages that make catalytic converter removal much more time-consuming, encouraging thieves to leave your car alone and move on to an easier, unhardened target. Another proactive way to discourage theft is to have your catalytic converter etched or engraved with your VIN or license number, making it easier to identify the owner.

A modern catalytic converter’s oxygen sensor measures how efficiently it is doing its job by monitoring the amount of oxygen present in the exhaust gases. Over time, and possibly due to some engine-related issues like coolant leaking into the cylinders, a bad gasket, or a too-rich fuel mixture, the oxygen sensor can become contaminated or just wear out. In addition to this “downstream” oxygen sensor connected to the catalytic converter, there is usually an “upstream” or “pre-cat” sensor that controls the fuel supply to the engine. 

Some indications that your car’s oxygen sensor is failing can include rough engine operation, reduced fuel efficiency, and the Check Engine light on your dash lighting up to alert you there’s a problem. And while you can clean a car’s O2 sensor, it’s not a great long-term idea. To identify the problem with your oxygen sensor, a diagnostic device should produce some trouble codes to guide you along. Make sure that there are no leaks detectible in your fuel injection system or your exhaust manifold, also checking the state of your ignition system parts. Once that you have properly diagnosed the problem and identified which of these sensors is faulty, the bad one can be replaced and correct engine operation restored.

The role of the oxygen sensor in your car’s emission control system, when operating properly, cannot be overemphasized. By consistently monitoring the flow of your car’s exhaust gases, it keeps emissions in check, maximizes performance, and gives you the best possible fuel economy.