How to Bypass Catalytic Converter Check Engine Light?

That day, I was supposed to go somewhere, and after starting my vehicle, I heard a loud boom!! Sound while the catalytic converter’s check engine light is illuminated on the dashboard. I couldn’t but check what was going on with my exhaust. I was half expecting my catalytic converter got stolen. But to my utter surprise, I discovered that my catalytic converter was there.

Yes, it’s a fact. Your catalytic converter might not be stolen, but still, your catalytic converter might not work efficiently, which could result in the check engine light staying on. Don’t worry. I will show you how to bypass the catalytic converter check engine light so it won’t stay illuminated on the dashboard.

check engine light still on after changing catalytic converter

Bypass Catalytic Converter Check Engine Light Step-by-step

The best situation you can ever be in when faced with a problem is knowing how to deal with it effectively. This helped me when I realized I now have a catalytic converter delete; even though the delete was unintentional, it happened anyway. I knew the check engine light would come on and stay lit without a catalytic converter, but I have knowledge of how to bypass it. The thought that I could at least fix the problem with the check engine light gave me confidence.

Well, maybe you have the same problem I did, or maybe your catalytic converter wasn’t stolen but is faulty. Anyway, if you have a reason to change your catalytic converter, but the check engine light is still on after changing the catalytic converter, you need to know how to get rid of the catalytic converter code using a code reader. Then the check engine light will turn off after getting rid of the code. In situations where you need to bypass the catalytic converter with a straight pipe, you also need to know how to bypass the catalytic converter check engine light so it does not stay illuminated on the dashboard.

When mine was stolen, I didn’t get a new catalytic converter; instead, I bypassed it with a straight pipe because I was worried someone might steal it again, as I didn’t have a secure garage at the time. I want to explain how I fit in the straight pipe using my catalytic converter bypass kit instead of installing a new catalytic converter. Still, in this article, I will only provide you with a step-by-step guide on how to bypass the catalytic converter check engine light.

Let me start!

Follow the procedure below:

  • Observe the dashboard for the check engine light and be sure the catalytic converter is the reason why the light is on.
  • Get a new catalytic converter if you can, or bypass the catalytic converter with a straight pipe using a catalytic converter bypass kit.
  • If you bought a new catalytic converter, after installation, clear all catalytic converter codes. But if you replace the catalytic converter with a straight pipe, continue with No. (4).
  • After fitting the straight pipe into the position of the Catalytic converter, you need to buy a spark plug defouler.
  • If you can get a long spark plug defouler, that’s fine, but if you can only get the short ones, you need two of those.
  • Unfasten the rear oxygen sensor, fit it into the spark plug defouler, and screw it in. (if you get two short spark plug defoulers, you should screw the defoulers together first.)
  • You might need to drill one of the defoulers a bit so the sensor can fit adequately after screwing the sensor into the defoulers. Screw back the defoulers into the exhaust properly.
  • Clear the codes with a code reader or drive around after some time; the light will turn off.

Follow the procedure above if you are looking for how to bypass a catalytic converter with an o2 sensor in it. This is just how I bypassed my catalytic converter without the check engine light staying illuminated before I bought a new catalytic converter after I got myself a safer parking spot.

catalytic converter cleaner check engine light

Pros and cons of bypassing the catalytic converter check engine light


  • Bypassing the catalytic converter check engine light is cheaper than buying a new catalytic converter. In that case, clear catalytic codes if all you want is to get the light turned off
  • Before bypassing the check engine light, if you did a catalytic converter delete because your catalytic converter was clogged, you will experience a slight increase in Engine power and better fuel efficiency.

Read Also: How to Find Catalytic Converter Scrap Value By Serial Number


  • You might not pass your state emission test if you bypass your catalytic converter check engine light.
  • You will always get false information that your catalytic converter is doing fine even though you know it’s not there. Therefore, excess harmful gases will continue to escape into the environment.
  • Catalytic converter deletes, and downstream O2sensor bypass is illegal in most countries.


Does removing the catalytic converter turn on the engine light?

Removing your catalytic converter will turn on engine light. If you start your engine after you bypass your catalytic converter, the engine Light will remain illuminated because the oxygen sensor is not getting its expected reading from the rear exhaust position.

Can I drive my car with the check engine light for the catalytic converter?

You can only drive your car with the check engine light for the catalytic converter if the catalytic converter is not leaking or clogged. If vehicle symptoms include loud exhaust noise and reduced engine performance, then you either have a leak somewhere (loud exhaust noise) or your Catalyst is clogged up(reduced engine performance), and you need to have the car checked by a mechanic.

If the car is still running fine without any of the above symptoms, you can still drive your car for a short time. But remember to have the vehicle checked by a professional mechanic when the light is on so you can know the actual condition of your catalytic converter.

What is the alternative to a catalytic converter?

If you can’t afford a new catalytic converter and are still a victim of catalytic converter theft, you might consider a catalytic converter delete. This is a process where you remove your catalytic converter and replace it with a pipe(a straight pipe of the same length). However, you must understand that there is no natural alternative to a catalytic converter because the function of reducing pollutant emissions coming out of the vehicle exhaust into the environment can only be provided by the catalytic converter.

Will an O2 sensor work without a catalytic converter?

The O2 sensor will still work without the catalytic converter; it will just continue to signal that the Catalytic converter has issues and need to be checked. As a result, the check engine light will stay lightened on the dashboard. To avoid the check engine light staying illuminated, this is why the O2 sensor is usually bypassed after the catalytic converter deleted.

Can I drive with the P0420 code?

You can drive your car if you do not notice reduced engine performance or signs of exhaust leaks. Code P0420 informs you that the bank 1 Catalytic converter system efficiency is below the threshold, which means the Catalytic converter might be clogging up. However, this code can also appear if your oxygen sensor or its circuitry is malfunctioning.

Final Words

The Check engine light staying illuminated on the dashboard due to a problem with the catalytic converter is intended to alert you that there is an issue with your catalytic converter. Still, in situations where you already know the problem, you don’t need to be notified about this issue anymore, but the light won’t turn off until the issue is resolved.

You may decide to perform a catalytic converter delete; even though the delete was intentional, the light won’t go out. The check engine light problem may be fixed if the step-by-step guide is followed carefully. Even though it is not the best option to bypass the check engine light due to catalytic converter issues but sometimes that’s the only option we have.

Engr. Omogbolahan Adeosun

Engr. Omogbolahan Adeosun is an automotive mechanic with over nine years’ experience, He is the C.E.O of Invadars Automobile, and hails from Ado-Ekiti, Nigeria. He obtained his Engr. (Hons) degree in mechanical engineering from Federal university Oye-Ekiti, Nigeria. Engr. Omogbolahan Adeosun writings interest areas are mainly automobile with major focus on four-wheeled vehicles. He has worked as a freelancer for over four companies’ home and abroad. He is a member of a notable professional organization Nigerian society of engineers (NSE). And his professional aspiration is setting a pace and example for the upcoming engineers, to invest their time and knowledge in making his country a proud automobile producers.

Recent Posts