If you’re looking to do some work on your truck’s exhaust, you should be aware of how many catalytic converters your truck came with from the factory. If you want to make sure that your truck passes a smog test (which you’ll probably have to take to make sure it’s road-legal), you need to make sure it has the same number of catalytic converters that it originally came with.

In the case of the Toyota Tundra, this truck comes with either two, three, or four catalytic converters. The exact number depends on the generation of the truck. Older trucks usually have two, while it’s more common for newer trucks to have three or four.

Today, we’ll be going over some general information about catalytic converters that you might want to know, including how they work and what the laws are regarding catalytic converters throughout the various states.

What Does a Catalytic Converter Do?

Before we get more into the laws concerning catalytic converters, let’s take a minute to talk about catalytic converters themselves and how they work. This isn’t essential to know as a car owner or anything like that, but it’s never a bad idea to learn how the various components of your vehicle work.

As you surely know, cars with internal combustion engines produce various emissions as part of the combustion process. Engines produce toxic gasses like carbon monoxide, as well as numerous other gasses that contribute to the greenhouse effect. 

In the 1960s, the U.S. government implemented the first federal standards outlining how many emissions a car could legally produce. This lead to the invention of catalytic converters as a means of reducing engine emissions.

These federal standards also led to the implementation of periodic emissions control testing. The actual laws concerning vehicle emissions and emissions testing vary from state to state, but every state’s laws still have to meet the federal requirements.

Most cars have just one catalytic converter, but cars with dual exhaust headers will often have two. Some vehicles can have as many as four, as they’ll sometimes have two main catalytic converters and two smaller secondary ones for extra efficiency. 

How Does a Catalytic Converter Work?

A catalytic converter, as the name suggests, uses a catalyst to convert particularly harmful engine emissions into less harmful tailpipe emissions. Basically, catalytic converters take potentially dangerous compounds and split them down into less dangerous compounds that can be released into the air.

Visually, a catalytic converter looks pretty similar to a muffler. It’s essentially just a box in the middle of the exhaust system. Inside a catalytic converter, you’ll find the catalyst support, which is usually made of ceramic and resembles a cube or a cylinder with a honeycomb structure to allow the exhaust gas to pass through it.

The actual catalyst itself is a mixture of metals that is applied to the catalyst structure. As exhaust gas moves through the structure, it comes into contact with the catalyst. The catalyst causes a chemical reaction in the exhaust gas, causing the harmful components in the exhaust to break down.

Catalytic converters usually have two types of catalysts; reduction catalysts and oxidation catalysts. Reduction catalysts reduce nitrogen oxide by splitting it into separate nitrogen and oxygen molecules, which are both harmless on their own. Oxidation catalysts add oxygen to carbon monoxide molecules, turning them into carbon dioxide (which is much less toxic).

Often, precious metals like platinum, palladium, and rhodium are used as the catalyst in catalytic converters. However, this has unfortunately led to criminals stealing catalytic converters from cars to get at the high-value components inside. 

What Should I Know About Passing an Emissions Test?

Depending on where you live, chances are you’re probably required to undergo periodic emissions testing to keep your vehicle road-legal. Obviously, part of passing an emissions test involves your vehicle having a working catalytic converter, among other things.

However, it might not be clear if your vehicle is going to meet the requirements necessary to pass the test, especially if you’ve modified your car at any point. For example, in California, you might fail an emissions test if your vehicle has a catalytic converter but that particular converter doesn’t meet the standards of the state.

In the end, the requirements needed to pass an emissions test are going to differ depending on what state you’re trying to get your vehicle certified in. That being said, every emissions test conforms to basically the same criteria.

At the very least, if you’re taking an emissions test, your car needs to have the following to pass:

• At least one catalytic converter
• Working oxygen sensors
• A working EVAP system to eliminate fuel vapors from the gas tank
• A working EGR (exhaust gas recirculation) system, which routes some of the exhaust gasses back into the intake

If you want to know more about emissions testing in your area, your best bet is to get in touch with your local transportation authority and see what they have to say.

How to Pass an Emissions Test

If you’re feeling concerned about potentially failing an upcoming emissions test, that’s totally understandable. There are a lot of things that can potentially cause you to fail an emissions test, and it can be pretty tricky to catch every little thing wrong with your car before you take it in.

However, there are plenty of things you can do to get your car in better shape for an emissions test. Here’s what you can try:

• Changing your oil: Dirty oil can sometimes produce fumes, which might cause your car to produce more emissions than it normally would.
• Making sure your tires are properly inflated: Your testing center might do a dynamometer test, where your car’s wheels are placed on rollers to simulate high-speed driving. If your tires are underinflated, there will be a lot more rolling resistance. This means the engine will have to work harder to get up to speed, and produce more emissions as a result.
• Dealing with the source of any check engine lights: If your car shows a check engine light during testing, you will automatically fail the test. Many things can cause the check engine light to come on, so you might want to take your car to the shop to determine the source of a check engine light.
• Warm-up your car before taking the test: Your car’s catalytic converter will perform its best if it’s able to reach its optimal operating temperature. If you want to make sure your catalytic converter is performing well during a smog test, it’s a good idea to do 20 minutes of driving or so before you actually take the test.