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Does A Diesel Truck Have A Catalytic Converter? [ Answered ]

Does A Diesel Truck Have A Catalytic Converter? [ Answered ]

In order to counter rising car emission levels and the effect on the environment, laws mandating the use of catalytic converters came into place in 1974.

This precious component plays a huge role in reducing emissions by converting poisonous substances into less harmful gasses. However, in order to serve its purpose, a catalytic converter uses three precious metals – platinum, palladium, and rhodium.

While it makes them a popular target for thieves, gasoline cars usually suffer cat converter thefts. This might make you wonder if diesel trucks have catalytic converters at all. Well, they do actually have catalytic converters, but a diesel cat converter is different from that of a gasoline vehicle.

Does a diesel truck have a catalytic converter?

All standard fuel-injected vehicles manufactured after 1974 use catalytic converters, including diesel trucks. In fact, the combustion of diesel creates large amounts of toxic emissions too, and a catalytic converter is crucial in any diesel vehicle.

However, a diesel truck’s catalytic converter differs significantly from a gasoline truck’s. It functions using a completely different mechanism and holds much lesser scrap value.

The difference is the result of the fact that diesel combusts differently than petrol, and has a different kind of emission. Diesel emissions contain large amounts of soot, or particulate matter.

Car manufacturers had to adapt the cat converters to make them suitable for diesel vehicles. This is why we have different catalytic converters for gasoline and diesel cars.

Do diesel trucks have catalytic converters stolen?

While gasoline vehicles ignite the fuel with a spark, diesel vehicles do it through compression. Hence, it isn’t necessary for diesel trucks to have catalytic converters as large and expensive as gasoline cat converters.

As diesel cat converters contain much smaller amounts of precious metals, their scrap value is lower too. Unlike gasoline cat converters, diesel cat converters do not contain rhodium. As a result, they turn out to be a less preferable target for thieves looking for these components.

Thieves generally target catalytic converters that are worth the effort, i.e., offer enough scrap value. They usually leave diesel trucks alone because selling a diesel catalytic converter won’t fetch them much money.

However, although it’s uncommon, catalytic converter theft also occurs in diesel trucks. Trucks have high ground clearance, which makes it easy for thieves to slide underneath and remove the component. Even if the scrap value isn’t much, the ease of stealing a cat converter from a truck may attract thieves.

Hence, although the risk of theft is low, your diesel truck isn’t perfectly safe. It would be wise to install protective equipment and take other necessary measures to deter thieves. This is especially crucial if your truck has a cat converter with somewhat decent scrap value.

How much is a diesel catalytic converter worth?

A number of factors affect the scrap value of a diesel catalytic converter. This is because different cars have different cat converters, and the quantity of precious metals can vary.

Although they aren’t as valuable as petrol cat converters, some diesel cat converters can still fetch decent scrap value. At the same time, certain diesel trucks have catalytic converters of such poor value that you might not even find it worth taking to a scrapyard.

The scrap value of a diesel catalytic converter can vary from anywhere between USD 10 and USD 800. On an average, these cat converters have a scrap value of around USD 388.

It all depends on the type of catalytic converter and the quantity of precious metals contained inside. Hence, even if you own a diesel truck, you still be able to get a good scrap value for its catalytic converter potentially. This is also the reason why thieves target diesel cars sometimes.

Where is the catalytic converter on a diesel truck?

Although catalytic converters on diesel trucks function differently compared to those on petrol trucks, their location remains the same. They are usually a part of the exhaust system, lying before the expansion box and after the exhaust manifold. This means a diesel catalytic converter is as easy for thieves to access and steal as a petrol cat converter.

Its size and structure may vary depending on the catalytic converter. This can cause a diesel cat to look different compared to another.

Also read:

  1. Cracked catalytic converter: Know all it about

How Long Will A Diesel Catalytic Converter Last?

Catalytic converters are usually quite tough, with impressive corrosion resistance. As long as your truck receives adequate care, its cat converter should last quite long. On an average, diesel catalytic converters have a lifespan of 10 years.

However, this isn’t an exact estimate, as various factors can impact its lifespan. Unless you become a victim of catalytic converter theft, your diesel truck would usually need only one cat converter replacement in its lifetime at most.

Factors that can impact the longevity of diesel catalytic converter

Although a diesel catalytic converter should generally last quite long, various factors can potentially reduce its lifespan. Here are some of the factors that can shorten or extend the lifespan of the catalytic converter of your diesel truck:

1. Emissions

Manufacturers design catalytic converters to deal with certain emissions. However, in case the emissions of your diesel truck include anything the cat converter can’t handle, it may lead to problems.

For instance, if your engine isn’t burning the fuel properly and the exhaust fumes contain leftover fuel, it may clog up the catalytic converter. This will make the component lose its efficiency, and eventually fail.

2. Stop-start duration

The length of your trips also affects the lifespan of your diesel catalytic converter. When you make short stop-start journeys, you have to switch off your engine before the cat converter can reach its optimum temperature.

Doing so regularly can cause the component to wear out faster. Eventually, you may end up having to replace it with a new catalytic converter.

3. Damage

Although a catalytic converter is a tough and durable component, it’s still prone to both internal and external damage. If the component suffers damage, it can reduce efficiency or stop working altogether. You should take special care to protect your truck’s cat converter from damage, as a replacement can be costly.

4. Usage

How much you drive the truck every year would also affect the lifespan of its catalytic converter. While a cat converter has an average lifespan of 10 years, it’s true only when you drive your truck for about 10,000 miles every year.

A more accurate measure of a cat converter would be in terms of mileage – an average diesel cat converter lasts 100,000 miles. The cat converter’s lifespan may vary depending on whether your actual usage of the truck exceeds or falls short of the average yearly mileage.

How does a diesel catalytic converter work?

A diesel catalytic converter is not the same as a petrol catalytic converter. You might be wondering how a diesel catalytic converter actually works. Let us first take a look at the components of a diesel catalytic converter:

  • Diesel oxidation catalyst (DOC): This component is very similar to a gas catalytic converter, although it doesn’t contain any Rhodium. The purpose of the DOC is to reduce carbon monoxide into carbon and water. It also helps in breaking down hydrocarbons into less harmful substances.
  • Selective catalytic reduction (SCR): The SCR makes use of an ammonia-based catalyst to break down nitrogen oxide, an extremely toxic gas. Through the reaction, NOx breaks down into nitrogen and oxygen. This is a crucial component that can reduce the NOx emission of a diesel vehicle by 75% to 90%. Closed-loop SCR can deliver more than 95% reduction of NOx. Although it also helps break down hydrocarbons too, the SCR is less effective at it than the DOC.
  • Diesel particulate filter (DPF): Emissions from diesel engines contain significant amounts of particulate matter, especially due to the presence of sulfur in the fuel. Such particulate matter can cause severe environmental pollution. To filter them, diesel catalytic converters come with a special component – diesel particulate filter (DPF). The DPF captures the particulate matter using a wall flow monolith and holds them. Platinum and palladium present in the DPF act as catalysts to break down the particulate matter and remove them through a process called ‘regeneration’.

Do note that there are two major types of diesel catalytic converters – two-way and three-way. The three-way catalytic converters can regulate and reduce all three harmful substances – carbon monoxide, nitric oxide, and hydrocarbons. However, two-way cat converters aren’t as advanced and cannot break down nitric oxide.


Catalytic converters on diesel trucks may hold much less value than petrol cat converters, but they are still equally important. Without a cat converter, a diesel engine would cause severe pollution, with the exhaust gasses carrying soot in addition to the toxic gasses.

A missing catalytic converter in a diesel truck requires an immediate replacement or the truck would fail emission tests, and you may face fines. Hence, even though the chances of theft are low for diesel cat converters, you should still take measures to protect the component.