Code PO420, catalytic converter issues

Tiny
RICH1966
  • MEMBER
  • 2004 HYUNDAI SONATA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
I replaced one of the three converters. All 4 02 sensors. Code Po420 came on. I used catty clean worked for a couple days then code came back on. Was wondering if I could use catty clean again or should I just replace the other 2 converters? Can't really afford them at the money. Car won't pass inspection.
Thursday, May 13th, 2021 AT 2:42 AM

2 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

I attached the flowchart for you of the code below. In most cases, the catalytic converter is the issue. I attached a picture of the location for you.

https://www.2carpros.com/articles/catalytic-converter-replacement

I also attached the part from Walker for you as well.

Roy
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Thursday, May 13th, 2021 AT 3:24 AM
Tiny
HARRY P
  • MECHANIC
  • 2,291 POSTS
Hello. You can try that again. But my suggestion would be the old "seafoam trick." Basically, you buy a can of seafoam at the parts store ($7.00). Go home and when no one is around (neighbors included), you start the car, open the good, pull the brake booster vacuum l okay be, and stick it in the seafoam bottle until it sucks up all of the seafoam. The car will smoke like a chimney. Turn it off one the seafoam is all gone. Let it sit a while (at least 30 minutes) and then go for a drive. Drive it like it's stolen. Clear your codes. They'll probably stay gone for a few months. Here's a YouTube video:

https://youtu.be/4VOr2LviTnQ

Don't drink seafoam. Please. Just let your car drink it instead. There are some other tricks we can try, but this is the most legal and cheapest one so let's start with it.

PS - This will not completely fix the problem. It just buys you some time. It is most definitely a backyard kind of trick and most shops will not do it for you. It is not generally accepted practice, but it does work.
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Thursday, May 13th, 2021 AT 3:45 AM

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