Hi all, I know I'm beating a dead horse with this quick thread, but I need some clarification.
2006 F150 5.4
133,xxx miles

I have a P0420 code since I bought the truck. I cannot feel any misfires nor do I get a flashing engine light for any. Only thing that I do not know is if I have power loss, since the truck is new to me then I don't know what it "should" feel like.
I've hooked up my scanner to watch the voltage on the O2 sensors. Both bank 1 sensor 1 and 2 are graphed together live. After warmup, essentially sensor 2 mimics sensor 1. I found that on the driver side (bank 2) the second O2 sensor does not mimic the first sensor (properly reading with a good cat from my understanding).

So to sum up I've got the P0420 code for bank 1, and I'd like to get some pointers from the wizards on here to help with what I should start with. Is it a clogged cat, broken cat, O2s... I've just recently ordered some new boots and springs,, and some new Sp546 plugs.

Thanks dudes.

 

Could be faulty downstream 02 sensor. Or a partially clogged cat. Just spitballing

 

yeah I guess I'm trying to understand whate EXACTLY causes sensor 2 to mimic sensor 1.

 

Do you smell rotten egg from your exhaust? clogged cat will stink and get red hot...

 

On my 2007 F-150 4.6L 2v I had a similar situation. When I bought the truck used about 3 years ago it had a check engine light and a P0430 code (like your P0420 but other bank). Truck performed well so I attended to immediate concern which was transmission issue with no reverse gear. After I fixed the trans I played with different solutions to the P0430 while avoiding, due to assumed cost, replacing the catalytic converter on drivers side. Nothing cleared the code so I finally bought a new catalytic converter.Changed Bank 2 catalytic converter and P0430, Faulty Three-way Catalyst Converter Bank 2 is still present! This was not expected. Catalytic Converter-Direct Fit Left Eastern Mfg fits 06-08 Ford F-150 4.6L-V8 was ordered from e-bay $162.
However later, Check Engine light has been off for more than a month since I changed the Bank 2 catalytic converter. Update – 08/05/2021, the Bank 2 catalytic converter that was removed was taken to a recycle center and it was determined that it was empty. Bank 2 catalytic converter was empty when I bought the truck thus the continuous check engine light.

 

When the Catalyst material is unable to "capture and store" OXYGEN, the downstream _sees_ the change in fuel / air mixture as the upstream sensor. Thus, the rear O2 sensor mimics the front.

The PCM intentionally and normally varies (increases and decreases) injector pulse width to richen up and lean out the fuel / air ratio ~several times a second. A reading of 0.45 volts on a calibrated / good working O2 sensor represents the perfect fuel / air mixture (14.7 : 1) where there is no (or minimum) unburned fuel in the exhaust. That should be the average (RMS) front O2 reading. (Zero volts [actually 0.1v] represents presence of oxygen, One volt [actually 0.9v] represents absence of oxygen).

The material in a proper functioning CAT has the unique ability to "Capture" and "Store" Oxygen --- and that oxygen reacts (burns off) the excess hydrocarbons that were NOT consumed during the combustion process and expelled into the exhaust. As the CAT burns up the hydrocarbons - the Oxygen it had stored is consumed (mostly). Thus the rear O2 sensor would produce generally a higher reading (near 1 volt) [generally around 0.7].

Under heavier load or coast conditions, the CATs cannot handle the abnormal fuel/air mixtures. So - CAT codes are ONLY an indication whether the CAT is operating AT-ABOVE or BELOW a genera spec depending on specific exhaust configuration of your vehicle (Single / Dual / Y-Pipe). The OPTIMUM driving conditions for the CAT to function and the CATSTAT emission status to become true is light cruise - urban freeway driving.

Cats can - and do - become contaminated with stuff like excessive engine Blow-By, or some fuel additives, or antifreeze from a leaky intake manifold gasket (-recently happened to me).

You could try to 'Clean' the cats by running a FULL gallon of pure Acitone in each of two full tank of gas. I did this to mine (@ 250,000 miles) and got rid of a CAT code. It can work if the guts of the cat have not been melted from neglecting the condition (such as flashing CEL) for too long.

Good Luck

 

TL;DR



There's nothing wrong with the O2 sensors.

Chemically "dead" cat. It ain't "converting". Could be that the cat's been "gutted".

 

No rotten egg smell from what I can tell, and the cats seem to be ok as far as temp, however the IR temp gun I have seems to be useless.

 

If the tool is useless, then any observation (or conclusions drawn from those observations), are also of the same value.

 

sounds like a new cat is in order