Need good advice -P0420 Q's
 

2005 F-150 5.4 45,000m
runs like a top, no hesitation, or missing

-Check engine light came on and mechanic read a P0420 code.
-He changed the front two 02 sensors (bank 1 sensor was black) and thought problem was solved.

-2 days later the CEL comes on again.
-Mechanic talked to some Ford mechanic friends and they figure the Catalytic Convertor may be plugged.

-I went to Ford dealer and he said the Cat is only warrantied if it is 'broken', and not if it is 'plugged/blocked'. Testing the cat for blockage is $100.

-Called another Ford Dealer (miles away) who told me that there would have probably been a reason to cause the blockage at that mileage. I mentioned that 3 injectors broke 8 months ago and he said that may certainly cause a blockage. I made an appointment with the second dealer and he told me to make sure I bring the receipt in for the FI fix (helps toward a emissions warranty claim)

***SideNote - I don't trust the first Ford dealer I dealt with. When I had them fix the 3 fuel injectors they did not tell me that there was a hidden warranty on the FI's. He was very willing to take $700. from me. After some searches on this site , and other sites I found the extended warranty and am $700 ahead, thanks. When I went there the other day to enquire about the emissions warranty I was given the run-around by a smug Service Manager. (I went there because it is near my mechanics shop) I'll never go there again.

Can anyone tell me if this sounds like a Cat Conv blockage? or am I going to pay the $100 test fee for nothing? As stated, the truck runs perfectly.

Thanks for any replies,
Karl

Are there any performance issues like hesitation when you floor it? Any misfiring? Generally, when you have a plugged Cat you will get hesitation under heavy engine load and misfiring. If it's just a check engine light and no other symptoms it's probably bad sensors.

code p0420
 

Three months ago had plugs changed, fuel filter changed all four 02 sensors changed. I have a 2004 Ford F150 Lariat 5.4 Triton. 128,000 miles. Bought the truck used with 104,00 miles on it two years ago. Was told just had tune up. Noticed mild cutting out so I just decided to change everything. Since then I have had a code po506. Was told it was the idle air control valve. Discoverd that I did not have one on this truck. So, I took the body throttle apart, cleaned it and replaced air filter. Code went away. Drove over 600 miles and check engine light comes back on. This time the code is PO420 catalytic converter. Truck does not cut out, idles great and runs like a scaled dog or cat. Cat. seems to be fine, not making noise, rattling, etc. ANY SUGGESTIONS? my friends.

I had the same but for the other bank (P0430). I changed the cat and the code hasn't come back. The truck ran fine through out the year the code was there except for when the plugs started going bad. I bought a universal Magnaflow for $63 and had it installed for another $50. A hell of a lot cheaper than OEM replacement.

Dan J can you tell me what was the product number and where you bought your CAT from. I'm having the same issues. The muffler shop said today that it would be $1000 for one.

I bought a Magnaflow 94036 but it was actually the wrong one because it has 2 1/2" openings and I needed 2 1/4" . The guy at the muffler shop made it work though.
I bought mine at Performance Peddler for $63. The Muffler shop charged me $50 to install it. You might want to call Magnaflow to get the correct part number. Performance Peddler's site sucks for giving you the correct part number. I know there is the same cat with 2 1/4 openings but I can't find it again.
Good Luck!

P0420 is a bad cat, doesnt mean its clogged by any means just means its not doing its job anymore. 3 fuel injectors breaking would cause it, if they dumped raw fuel into the cat it will melt the catalyst inside.

I've had many cars come in to the shop with P0420 and P0430 codes. They need a cat and there is no way around it. A plugged cat may not even put out a check engine light as the rear 02 wont see as much gas thus the sample its taking is smaller and it thinks the cat is actually working better. However after a test drive it becomes obvious that the cat is clogged as it becomes a guttless turd on the road.

At that mileage you should beable to get them under warrenty, however with 3 failed injectors I dont know if they will warrenty it. The Emissions warrentys are usually 8 years 120000 miles

Hopefully he got it fixed by know since the OP's post was from 2009. :)

Nope, 8/80, less in California.

have the same code right now. just turned 120,000 miles. whats the part # for the magnaflow?.

So Confusing. Which exact cats need to be purchased
 

i have the p0420 code. I always have, for 6 years now. replaced the two forward sensors, still bogged down and, shifting slowly and rattling like a MF will idled (highly noticeable while in drive thrus) To my knowledge my truck has four cats, which can all be removed somewhat individually and purchased separately. Just took the vehicle to Christian Brothers and they told me it'll be $3292.59 to replace "both of them" The diagram they gave me has a picture of the two larger cats that eventually lead into one pipe that leads to the single muffler. I have a friend who says he can get me both of those same two cats for a damn good deal of $325. The mechanic at the shop then told me that it the Driver side and Passenger side forward cats aren't actually cats. Then what are they? From the Headers on each side there are two cats and two sensors and then down the line on each side there is another larger cat, say beneath the front seats with two more sensors before they come together and lead to the muffler. My question is when there is a bank 1 error code, which of those four cats is it saying is having issues? Is it one of the two smaller forward ones directly after the headers or one of the two larger( longer with more pipe ) ones that are beneath the front seats? To further confuse me when i go to FORD and look up my VIN they show me the option to purchase ONLY TWO CATS assemblies which look to each have two cats upon it ( a forward and rear on each assembly). They want even more for those two parts which apparently have the two cats per assembly. Did ford upgrade the design? Am I an idiot? Are there not FOUR cats on this puppy? Some people refer to the two forward ones as Pre-Cats. whatever the hell they are called, I'd really like to know which part i need to replace? There's close to a 1000% difference in the pricing im being given and all i want is to get the right item replaced. On Autozone they show the exact two parts that i think i need to purchase for roughly $350 each.. What the Christian brothers showed me (part 5E212A & B) looks identical to what Autozone (Part 50553 and 53569) shows matches my vehicle then theres the ones that FORD says i need to buy (Catalytic Converter - Ford (4L3Z-5E212-CE) come as a combo with two cats per unit and $1600 EACH!

Heres my VIN 1FTPW145005FA50913 2005 fx4 5.4l Triton 232K

Do you have 49 state emissions or California emissions?

Look through this:

https://www.rockauto.com/en/catalog/...converter,5808

P0420 is bank 1, that's passenger (right) side.

I have the 49 state, and I've been advised to buy only oem and to specifically stay clear of RockAuto. the 50553 and 53569 they have listed for the 4WD look to be what I THINK I need, look just like the ones on autozone and the b5212a/b one on the diagram they gave me. the 30495 /4 look like the combo two n one parts for $3200 that ford website says fits my truck.

Why avoid Rock Auto? They sell name brand parts. Walker is decent quality. I've also had good luck with Eastern Catalytic. They both have 5/50 warranties.

Rock Auto is amazing. I very recently ordered $3k worth of parts for other people's vehicles on there. MOST came in the following day and ALL parts were EXACT replacements.

Rock Auto beats most everything.