The $10 Catalytic Converter Fix You Can Do…But Shouldn’t

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Do you have a check engine light and P-code indicating your catalytic converter may have gone bad and will need an expensive replacement? Here’s a fix you can do to avoid buying a new catalytic converter…but should not.

In previous articles we have learned why catalytic converter theft is such a huge problem should you be unlucky enough to fall victim to this crime. Not only will you need a replacement catalytic converter that may be prohibitively expensive for a used car, but the fact is that other damage is often done to the car during the theft.

In the real world, there are non-theft related problems as well with replacing a catalytic converter on not just a Lexus (as shown in the video below) but in many other models as well---especially when your mileage is getting past 150,000 miles or so. Certainly, for those situations when the problem goes beyond being an inconvenience and becomes an impossibility for many who are struggling to make ends meet. Worse yet, you might live in a state or county that requires emissions testing and will fail you if your car has a catalytic converter problem.

The Dreaded P0420 Code

According to a recent Mike the Backyard Mechanic YouTube channel episode about an illegal catalytic converter fix, that check engine light and a P0420 code can be due to multiple reasons aside from a bad catalytic converter. Such as:

  • A misfiring engine
  • Leaky fuel injector
  • High fuel pressure
  • Using leaded fuel
  • Faulty rear oxygen sensor
  • Damaged oxygen sensor wiring
  • Damaged or leaking muffler
  • Damaged or leaking exhaust manifold
  • Damaged or leaking exhaust pipe
  • Oil contamination in the catalytic converter
  • Faulty engine coolant temperature sensor

However, most of the time it is due to a failing catalytic converter.

Signs and Symptoms of a Catalytic Converter Gone Bad

  • Check engine light turns on
  • Reduction in fuel economy
  • Dip in engine performance
  • Foul odor coming from the exhaust
  • Car fails emissions test
  • Rattling noise coming from underneath your vehicle
  • Dark exhaust smoke coming from your car’s tailpipe leaves a residue behind

A Questionable Solution on Several Levels

One solution for a quick and easy fix is to try one of any number of mechanic-in-the-bottle solutions that are reputed to “clean” your catalytic converter well enough to pass an emissions test…or dupe someone into buying your used car that has a check engine light warning for a catalytic converter issue.

However, a mechanical solution is to alter the sensor by adding a spacer to it so that the sensor gets minimal readings of the exhaust without triggering a fault by the engine’s computer.

Follow along with the host as he demonstrates how easy it is to do this fix on his Lexus and then be sure to read the discussion below the video.

Why Share This Video?

First off, I would like to say that this “fix” goes beyond jerry-rigging a repair, of which I am not a huge fan of. The correct repair with the right tools and parts is my recommendation—always. Except in times of an emergency.

This “fix” is illegal. A quick search on the internet reveals that “…permanently removing, bypassing, or destroying your car’s pollution controls is against state and federal laws and if caught can result in either an expensive fines or jailtime, or a combination of both.”

In the eyes of the law, this is no different than doing a “cat delete” as reported in an earlier article titled “Should You Consider a Catalytic Converter Delete?”

The value of this video and why it is shared is that it alerts used car buyers to the fact that this is one of many tricks unscrupulous used car sellers’ resort to that you should be wary of whenever buying a used car. If you hire a mechanic to do a prepurchase inspection, you can ask him or her to look for evidence of this…just in case.

For related articles, here are three useful repairs or fixes you can do legally on your car:

Bonus Video: Removing Catalytic Converter: Pros and Cons

Timothy Boyer is a Torque News automotive reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on Twitter at @TimBoyerWrites for daily new and used vehicle news.

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