Based on statistics from Highway Loss Data Institute (HLDI), the risk of theft of a Toyota Prius catalytic converter has increased 40-fold since 2016. It is because newer Prius models feature cats with great material value.
Many Prius owners are continuing to drive their vehicles despite having their catalytic converters stolen. Unfortunately, this can be detrimental to the cars.
Driving without a catalytic converter leads to poor fuel economy, harmful gas emissions, and unbearable noise in your Prius. You may also be fined if the converter is missing from your car.
In the article, I outline all the reasons why you should reconsider driving your Prius without a cat. I will also provide an estimate of what it might cost to replace the catalytic converter.
Let’s get started!

Can You Drive Prius Without Catalytic Converter?
Technically speaking, yes, you can certainly drive your Prius without a catalytic converter.
But would I recommend it?
No, and even if I did, I would suggest getting your car fitted with another cat as soon as possible.
This is due to some fairly straightforward reasons. First and foremost, it is unsafe and has numerous disadvantages, including poor mileage, unstable acceleration, etc.
You can learn more about the drawbacks of driving a Prius without the cat in the following section.
What Happens If You Drive A Prius Without A Catalytic Converter?
The list goes on and on about why you shouldn’t drive your Prius without a cat. Some of them are more serious than others. Let’s take a look at them all below.
1. Bad Fuel Economy
The unmatched fuel efficiency of a Toyota Prius is a paramount reason why it is so popular. Unfortunately, the efficiency drops dramatically if no catalytic converter exists in the system.
Whenever the ECU cannot detect the cat, it switches to a default fuel-air mixture. This results in poor fuel economy.
2. Loud Exhaust Sound
One of the responsibilities of a converter is to muffle exhaust sounds as much as possible. When you don’t have it in your Prius, the car will be horribly loud.
I understand that many folks would prefer loud sounds. However, I assure you that you won’t enjoy the loud noise caused by the absence of catalytic converters.
It is obviously incredibly loud, but the raspier tone makes it even worse.
3. Unsteady Acceleration
The converter regulates exhaust as efficiently as it can. As soon as your vehicle is missing this essential component, the exhaust will be unregulated.
This can lead to inconsistent acceleration and a frustrating driving experience in general. For example, you will often experience jarring when driving.
4. Failed Inspection
To drive your Prius legally in the US, you need to pass the emission test. There is virtually no way for your car to pass this test without a catalytic converter.
Furthermore, the safety inspection check is another annual check. Catalytic converter-less cars are likely to fail this test as well.
Read Also: How To Pass Inspection With Bad Catalytic Converter?
5. Check Engine Light
It goes without saying that catalytic converters play a crucial role in exhaust systems. When it is not there anymore, the exhaust fumes can no longer be filtered.
Once the O2 sensors detect it, they will alert the ECU. As a result, the unwelcome check engine light will illuminate.
Catalytic Converter Replacement Cost For Prius
As you can see, driving your beloved Prius without a catalytic converter is a bad idea. In other words, if you are faced with theft, you have no choice but to replace the cat.
Sadly, the replacement cost for newer Prius models is quite expensive. You can expect to shell out around $2000-$3000 for the parts and labor to replace the catalytic converter on your Prius.
So why is the cost so exorbitant? The reason is that hybrid vehicles like the Prius typically have better cats than conventional cars. As a result, their replacement costs are also higher.
However, you are in luck if your Prius was manufactured between 2004 and 2009. Several high-quality yet inexpensive catalytic converters are available for these models.
Moreover, provided your Prius is insured with comprehensive insurance, replacing the converter won’t cost you an arm and a leg. The insurance company will cover the cost.
Is It Safe To Drive Prius Without Catalytic Converter?
It is not safe to drive your Prius when there is no catalytic converter in place. Let me elaborate on that.
You see, every vehicle emits harmful gasses such as carbon monoxide, hydrocarbons, and nitrogen oxides. The Prius is no exception.
This is where a catalytic converter comes in handy. The device transforms toxic gasses into less harmful substances like water vapor. It means that without a cat, hazardous gasses remain unfiltered.
Such unfiltered gasses pose a major threat to the environment once they escape the vehicle. Even worse, the driver and passengers of the Prius could suffer harm due to the toxic gasses.
Considering all this, I do not believe driving a Prius without a cat is safe.
Related: Does A Cat Back Exhaust Replace The Catalytic Converter?
How To Prevent Toyota Prius Cat Theft?
Here are two ways you can protect your Prius from catalytic converter theft.
1. Using a Protective Shield
To prevent cat theft, there are several protective devices on the market. However, the shield from Cat Security stands out because of its solid construction and security features.
It is also lightweight, meaning it won’t add too much weight. The shield also allows easy smog checks.
2. Using Alarms
Although Toyota Prius has alarms, they are ineffective in preventing catalytic converter theft. It is because these alarms do not have vibration sensors.
Nonetheless, you can install an aftermarket alarm that goes off instantly upon detecting vibration. Since removing a cat is labor-intensive, vibrations are sure to be picked up by the alarm at some point.
Related: Toyota 4Runner Catalytic Converter Theft: Tips on How to Prevent
To Sum Up
As the article indicates, there are a number of downsides to driving a Prius without a cat. The loud noise, low fuel efficiency, and rough driving experience are impossible to ignore, no matter what.
Hence, you should replace the converter as soon as you can, regardless of the cost.
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