raceknb

I just recently purchased an 09 XLT with the 5.4 3v. Shortly after filling it up, the CEL came on and gave me a p0420 on both bank 1 and 2. I looked under the truck and discovered that it has block to tail custom exhaust and the cats are gone. The O2 sensors are still intact but no cats. I reset the codes, and ran it. It will go for about 50 miles and then turn the light back on.
Has anyone else had this? I read the live data on the O2 sensors and all seems to be in order.
Wondering if anyone has an suggestions.

RLXXI

There are missing sensors usually located after the cats, they look identical to the upstream sensors but serve an entirely different purpose, that purpose is to monitor the cats for proper operation, obviously they won't work properly because they have been removed.
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RbnFl

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scott.0691

Before I bought my 2014 F150 FX4 Tremor I owned a Porsche Boxster...its very popular to de-Cat the exhaust and place dummy O2 sensors which trick the ECU into thinking there is O2 sensors...they are inexpensive and can be found online...If this is the case look into them.

Dautz

Two suggestions,

A tuner can get rid of cel's such as this one. Takes the cel's thrown by the computer and if it's not essential to the trucks main functionality it won't pop the cel.

Next, did you buy it from a dealer? Do not quote me on this one but you may be covered under this warranty (I haven't read the fine print nor do I know your mileage.) Epa has an 8 year /80000 mile warranty on catalytic converters. This may be something to look into more.

https://www3.epa.gov/otaq/about/faq.htm#warranty

raceknb

The truck has 160k on it. So the EPA won't apply. The upstream and downstream o2 sensors ore there, the cats have been removed and straight pipe welded in. I was looking at the MIL adapters for the Mustang but not sure if they will work, or if I would need to replace all 4.
It may be easier just to but new cats and have them welded back in. It's got good flow without them, and I am thinking I may have weak plugs or coils causing a misfire. Live stream data from the sensors seems to show they are reactive. But as with all used trucks, I'm sure I will be playing a guessing game or paying someone to hook it up to their fancy obdii. Mine only does so much.
I appreciate all of your input tho.

Tghkd1

Laughed way too hard at this Lmaooo

ARKSoft84

Simple fact, those downstream o2s are seeing that the cats are gone.

Either get the MIL eliminators or put new cats on.

The main function of the downstream o2s is to let you know when the cat is bad. Your truck thinks both of them are bad.