Skip the auto shop - Our mechanics make house calls

Q: The car shakes during braking and at stop lights, error code P0420

asked by on

Recently, the code P0420 came on. I have problems with my car vibrating at the stop light when I'm braking. It starts running normally again when it is in neutral or when I speed up. There are no changes in fuel economy. I think this shaking has to do with the error code. It indicates issues with a possible leak, the catalytic converter, sensors. Please give me some advice on what to do as I would like to know more about this code and my car shaking. Thank you in advance.

Hi there. The P0420 code you are getting can cause your car to run like this. The code typically means that the catalytic converter is failing or one of the oxygen sensors may be failing.

If it was the converter, then you would typically have a loss of fuel mileage and engine power. If you do not have those, then it may be a sensor. I typically start by installing a scan tool and monitoring the oxygen sensor signals as that will let me know if the sensors are failing. If you plan on having this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair your car’s Check Engine Light and shaking issue.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 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. The car shakes during braking and at stop lights, error 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: P0420 P0430 trouble codes

Hello. Thanks for writing in. The universal oxygen sensors, a bad connection, or a bad catalytic converter can all be the cause of the codes. If you can you access to a known good oxygen sensor and test it in...

Q: How do I use the Driver Information Center?

A small screen that is located at the bottom of the tachometer on the instrument panel is called the Driver Information Center, DIC for short. This system allows the driver to select what data is being displayed in front of...

Q: Evap large leak code

If you have a large emission system leak the best way to find the leak is to do a smoke test and put smoke pressure in the fuel tank and it will show the smoke out of the system leak....

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...
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...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...