Hi I need a little help with code p0420B , First off my truck is a 2000 4 x4 xlt ext.Cab. with 180,000 kms.Here is a little history. Last winter the engine lost all compression in #1 cylinder. So I installed a used engine and with new head gaskets and intake gasket.Along with new coils (Ford). and Plugs. The truck has work flawlessly for 6000 km. But now started to buck under load on the highway. I thought that it was just a bad coil or plug giving me a miss fire. Just not throwing any codes. So to day it finally throws a code, and to my suprise its. P0420B. I know thats the code for a converter. So here the question. Which converter is it. Or could it be related to a O2 sensor failer. What can I try ,other than change out the converter? Ps. I tried to do a serch but could not really find the same problem with a answer. I hope somebody can help.

 

P0420 tells you that your cat on the passenger side(bank one) is below effecient threshold.I,m having the exact same problem w/ my truck except i have both codes 0430 and 0420,banks one and two.I have the high flow cats on my truck and thats the problem.I've tried r&r the o2 sensors,that didnt work,I installed a set of mils,those didnt work,I turned off the rear o2 sensors w/ my Diablo tuner,that didnt work.In short,nothing has worked.With out knowing the history of your truck and new engine,you can test your o2 sensors to see if there bad and @ $50.00 apiece,you might look into it.Your cats may be bad,there is a way to test them but I believe you need a special gun that reads heat signatures to determine if your cat is bad or not.My cel has been on for a couple of months now and I'm still trying to turn it out.I believe short of replacing your cats and resetting the computer the light will not go out.I know its not what you want to hear,but I,m faced w/ the same problem.My truck runs fine,I havent noticed any difference in performance,yet.I hope this helped,good luck w/ your cats.

 

Thanks vince, I'll change out my 02 sensors, And I guess if that doesent work I'll change out my cat. Once again thanks for the reply.

 

Pyeman,check your o2 sensors first before you replace them,search the posts and you'll find the tesing procedure.Its an involved process,but if you dont mind spending $50.00 apiece for new sensors,then buy them.As far as your cat goes,I have no idea what Ford gets for a new cat,I bet they only sell them in pairs.I've thought about replacing my high flows w/ the front factory cat,but the $$ scares me.Sorry I couldnt be more helpful,I'm faced w/ the same problem on my truck.When I solve it,Ill let you know,good luck w/ your cats.

 

the new body are $1000 each.

 

I guess that cel is going to be glowing for a long while.

 

LOL

 

O2 sensors rarely, if ever, are responsible for cat inefficiency codes. Don't waste your time or money.

MIL eliminators, properly installed, will trick the PCM into thinking the cats are working. You can make your own for two bucks if you can solder.

The OP needs to fix the misfire that caused the original cat failure (loaded it with unburn fuel to the point is was contaminated).

Steve