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Dan, Technician
Category: Toyota
Satisfied Customers: 24571
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Code p0420 thrown. I have already replaced the rear oxygen

Customer Question

hi. code p0420 thrown. I have already replaced the rear oxygen sensor after the last cat.
JA: Is the air conditioner cooling properly?
Customer: yep
JA: What is the model/year of your Toyota?
Customer: cel trac off and vsc trac llights light. 2002
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: replaced the cheapest oxygen sensor so fae far
JA: Anything else you want the mechanic to know before I connect you?
Customer: nope
Submitted: 11 months ago.
Category: Toyota
Expert:  Dan replied 11 months ago.

Hello, my name is ***** ***** I'm here to help get your problem solved.

Expert:  Dan replied 11 months ago.

This code means the catalytic converter is failing or has failed. You can try a burn off procedure to clean it out but if that doesn't help it will need to be replaced. To do burn out procedure disconnect a spark plug or coil to disable one cylinder then hold rpm at 3000 for 5 minutes. The unburned fuel from disabled cylinder will go into converter and burn out debris. Let me know if you have more questions or if there is anything else I can do to help. Thanks.

Customer: replied 11 months ago.
Any spark plug. I assume this is the front coming down from the exhaust manifold?
Customer: replied 11 months ago.
The truck has 271k on it
Customer: replied 11 months ago.
It's also getting poor fuel economy
Expert:  Dan replied 11 months ago.

What year, model, make, and engine size of truck?

Customer: replied 11 months ago.
2002 Toyota 4runner automatic v6
Expert:  Dan replied 11 months ago.

Does vehicle seem to run fine or run rough? When is last time spark plugs were replaced?

Customer: replied 11 months ago.
I think the spark plugs were replaced recently. I am going to replace the afr sensor and I can throw in a set of of plugs at the same time
Customer: replied 11 months ago.
It seems to be running a bit rougher than normal. Getting this info 3rd hand from my gf. "Wonky" is not a great technical reference :)
Expert:  Dan replied 11 months ago.

I'd start with burn out procedure and replace spark plugs. If it was anything else such as a sensor there would usually be separate codes. Let me know how it goes or if you have more questions, thanks.

Customer: replied 11 months ago.
Expert:  Dan replied 11 months ago.

No problem, keep me updated. Thanks again and have a great day!