P0420 Code - Any Experience w/Sea Foam? - Honda Fit Forum : Honda Fit Forums
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Old 09-18-2020, 11:41 AM   #1
Junior Member
Join Date: Jul 2016
Location: New York
Posts: 3
Default P0420 Code - Any Experience w/Sea Foam?

Hi Everyone,

We have a 2016 Honda FIT LX and recently have had issues.

She has 119k miles and is primarily used for highway mileage to/from NYC.
Recently the engine light came on, and the code is P0420.
Research indicates it could be the CAT, but there was also a Honda Bulletin that showed there were faulty fuel injectors that caused the code to pop.

Our mechanic did test the fuel injectors and they didn't show an issue.
There is no power or mileage(epa) lost, still a peppy car.

We heard if you run a few cans of Sea Foam in the gas tank, it should help with the injectors and clean out the CAT.
Has anyone had experience, either good or bad, with this?

Also, does this seem normal that the CAT would go around 100k?
As a side bar, the rear struts are also leaking. When it rains!

Thank you in advance.
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Old 09-25-2020, 03:00 AM   #2
Join Date: Jun 2016
Location: Hawaii
Posts: 49

The cat efficiency code will come on if there's a loss in cat performance. You may want to check the emissions certification label under the hood and see if it's federal or California emission compliant. I've replaced cats for California emissions cars at 100K a number of times. You might want to take a look at the downstream O2 sensor PID and see what reading you have. Typically, the downstream sensor voltage will not fluctuate much if the cat is working properly. If the voltage goes up and down while running the engine at 2000-2500 rpm it could be a bad cat. Before replacing the cat, you may want to replace the downstream O2 sensor to eliminate that sensor as being a problem. When you do replace the cat, you probably want to replace all the O2 sensors as well to protect the cat from a lazy upstream sensor that can cause fuel ratio issues that can affect the longevity of the catalyst.
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