Skip the auto shop - Our mechanics make house calls

Q: My car shows trouble codes P0133 and P0420

asked by on

hello. I had my car serviced about 2 months ago the car's ob was throwing off a p133, p420 and p171.. I took it to the shop, the oxgen sensor was replaced. .I Drove the car for a couple of days and the ob was throwing off just p420, I was told that if i add catalytic converter cleaner to the fuel tank its going to clean the cataltic converter..so i bought the cleaner but a couple days later still get p420. Am thinking ok i might need a new catallytic converter, but since it's expensive i wait until a month later to try to have it replaced..before i have it replaced i check the ob with handheld scanner now am getting a p133 and p420. I should not be getting a p133 since i had the oxgen sensor replaced about a month ago. when i take the car back to the mechanic that replaced the oxgen sensor he tells me maybe i should replaced the catalytic converter first, that the p133 code might go away. i think he is jsut giving me the run-around..can u tell me what to do?? thanks

My car has 182000 miles.
My car has an automatic transmission.

A: Hi there: It appears as if you’ve got a lo...

Hi there:

It appears as if you’ve got a lot of miscommunication going on with your mechanic. Here are a few basics. First, anytime an error code is triggered, such as the P0133 OBD-II code the issue needs to be fixed and then the error codes need to be cleared with a professional digital diagnostic tool - not the basic hand held scanner being used. So, before you take it back to this mechanic to get more of a run around (which I agree you’re getting) contact a professional mechanic to complete a simple Check Engine Light inspection. This will allow them to pull all existing error codes, clear those codes and retest the system to determine what is wrong with your Corolla.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: How do I adjust the air outlets?

Your vehicle has four front air outlets: two in the center, and one on each side. All of these outlets can be adjusted up, down, left, and right, simply by grabbing them in moving them in the desired direction. The...

Q: The RPMs are extremely high when I try to shift gears.

Hello, One thing to keep in mind is that there are thee points of reference or sources of signal when the vehicle is shifting gears up or down. These are: the idle control valve, the throttle position sensor and the...

Q: How do I put on a seat belt correctly?

Wearing a seat belt can save lives, but only if it’s put on correctly. Otherwise, it can be dangerous in an accident. Pull the shoulder belt forward so that it extends over the shoulder but not touching the neck....

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...