P0420 code after filling gas tank

[johnboneske]

For the last 3 times I have filled up, as soon as I start my Expy I get a check engine light, and when I get home I scan it and get code P0420 Catalyst system Bank 1(dont remember exactly what it says). I ONLY get the CEL light after I fill up, it doesnt happen any other time.

I just replaced all the coil packs and installed new plugs this past summer, and also had the drivers side CATS replaced this summer also Which side is Bank 1? Drivers or Passengers? Thank you!

 

[Hamfisted]

Bank 1 is the passenger side. Can you read live data on your scan tool ? Compare the oxygen sensor readings between the sides. What lead you to replace the cats on the drivers side?



-Mike

 

[johnboneske]

My scanner doesnt read live codes I dont think. I replaced my cats on the drivers side cause the front cat honeycomb was loose for a long time and finally wore itself enough to turn inside the chamber and had LOTS of restriction. I wanted someone to weld up 2 aftermarket cats(one on each side) with the O2 sensors front and back, but no one would do it here for me. I paid WAY to much to get one side done... $600!! But, they are new and have a 5 year warranty.

 

[Hamfisted]

You can download Forscan and use it with your phone or laptop to read live data from your Ford. It requires one of the common ELM327 OBDII port bluetooth modules (ebay...or Amazon...).

https://www.amazon.com/BAFX-Product...?srs=4920137011&ie=UTF8&qid=1511583970&sr=8-1

http://www.forscan.org/download.html

https://www.amazon.com/BAFX-Product...nt-20&linkId=00fd85cc462c533a6c35879f3b32c519


-Mike

 

[plumcolr]

I suggest you check the vacuum lines and purge valve related to the EVAP control system. The vacuum hose between the intake and the purge valve on mine just sorta disintegrated. Possible that a bubble of raw gas is getting into system when you fill the tank and overwhelming the cat momentarily.

 

[rjdelp7]

PO420 is Cat operating below 97% threshold. It has nothing to do with filling your tank and its the driver side. I had same code and truck was running normal. I found an item, called MIL(malfunction indicator lamp) eliminators. It plugs inline with the rear O2 sensor. The rear O2 only check smog. The MIL's trick PCM with correct voltage. I installed one on driver side rear 3 years ago. No codes and passed inspection. You just have clear existing codes. Price was $18 and 5 min install.

 

[johnboneske]

yes, but I only get the CEL after I fill up. I put on about 300 to 350 miles a week on it and the light never comes on. After I fill it up at a station it comes on, every time...for the past 5 fill ups. I think it is "funky" it only happens after I fill it up and no other time...

 

[rjdelp7]

yes, but I only get the CEL after I fill up. I put on about 300 to 350 miles a week on it and the light never comes on. After I fill it up at a station it comes on, every time...for the past 5 fill ups. I think it is "funky" it only happens after I fill it up and no other time...

OK, are you clearing the CEL code? A CEL needs about 50 starts to reset, on its own. If you did it, you must drive 50 miles with some speeds over 50mph. That will close monitors, for OBDII. PO420 has nothing to do with fueling. It is a "California" emission failure. You may be over filling tank. The fuel can go into evap line and charcoal canister. Have you ever seen fuel dripping from driver side rear? That is bad. That is fuel in evap canister. Stop filling after 1 or 2 clicks.

 

[johnboneske]

Yes, I am clearing the code. I drive on the freeway daily, mostly above 50MPH, where is the charcoal canister located, along with the evap line? I usually "top it off" to the closest dollar amount, I have never seen fuel dripping from it on the drivers side either. So, it says P0420, is that drivers or passenger side? I get conflicting answers... I have new Cats on the drivers side(installed this past summer), same O2 sensors though. Will something like this work threaded into the back cats?

https://smile.amazon.com/Universal-...&qid=1511926222&sr=8-7&keywords=o2+eliminator

 

[rjdelp7]

Your vehicle self checks itself, that is catalytic converter operating correctly. PO420 is triggered when Cat is not at 97% or higher(thank you, liberal California). Basically the vehicle, will fail state emissions. I got a Evap 101 code after fueling and squeezing, another 1/2 gallon. They are not related, unless raw fuel is getting sucked into engine, via the evap line and getting dumped into the Cats. Try this, run tank down below half. Next time you fill up stop at 1st click. Fill vehicle, on a slight downward angle, not uphill.