Q: Diagnosed as code P0420

asked by on

The Engine light came on. I went to the mechanic an it was diagnosed as a code P0420.

When you get a P0420 code that indicates a failing catalytic converter. Most of the time that is exactly what it is. In some cases, it can also be caused by a bad oxygen sensor. I typically use a computer scan tool to monitor the signal coming from the oxygen sensors. If they are not reading correctly then they need to be replaced. If they are fine then the catalytic converter needs to be replaced. If you would like to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to make a diagnosis and to replace either your oxygen sensor or catalytic converter.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Diagnosed as code P0420

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Horn keeps on going off

Hello. There are a couple of reasons why your horn keeps going off. It is possible that one of the horn contacts is stuck or making contact in error. It is also possible that there is an issue with your...

Q: Car hesitates while accelerating, check engine light on all the time

The Check Engine Light going on and off is most likely caused by an engine misfire. The intake manifold could be leaking vacuum when it is cold, and sealing up when the vehicle warms up. The engine running poorly...

Q: Key not working

There are many questions that should be answered before diagnosing this type of question. Does the key not turn the ignition, or does the ignition turn but the engine will not crank, or does the engine crank but with no...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...