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.

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: Using the 3 2 1 Gears in an automatic.

They are there for a reason. The transmission is controlled by a computer. It will not let you cause damage. You have to look at it from a perspective that it's there to prevent shifts, and not to force a...

Q: im having trouble starting my car

If you feel like the vehicle is flooded, try smelling the tailpipe for gas fumes after trying to start the vehicle. You can also try putting the vehicle in "clear flood mode", or "clear out mode" by holding the gas...

Q: How do I stop my transmission from slipping?

This suggests low transmission fluid or possibly a faulty transmission control module. A faulty transmission control module may cause a delay in acceleration or erratic shifting of gears. The transmission control module has various sensors such as vehicle speed sensors,...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.