My coveted CE light is back on and I had Autozone read code;;;Po420.. says catalyst systen efficiency for bank one is below threshold for the current engine operating conditions....this means nothing to me ..any help will be appreciated...have 1996 f150 with 4.9 ...need some help ....Thanks

 

Could be you lost your oxygen sensor

 

replaced one last year back by the cat converter ....think that was one of two or three that i have...////????

 

It is for bank one, so I would guess it is the O2 sensor on bank before Cat?? I honestly don't know. either that or your catalytic converter is not work like it should. that will require a new cat. or you could take it to Ford or some other shop to find out what really is wrong with it. Throwing money at parts that may or maynot fix it don't help much and could cost more in the long run, and still not fix it. I suggest taking it in to have it checked out.

Scott

 

might take to another shop for another reading to see if i get same results..? this ce light has been going off and on for months now...

 

Make sure the engine isn't overheating, check the wiring to the rear O2s, verify proper fuel pressure, be sure there's no loose connections or anything like that, and if all that's good to go, you probably need a converter.

 

change the first o2 sensor the one that gets the hottest

 

The over heating issue ...what other option do i have except gauge? ...I installed a 2 row radiator one year ago ...gauge reads normal...i'll check wiring on o2 sensors ....last ce light that I got reading on was specific to the o2 sensor that was back by the cat converter...THANKS

 

Well, if the engine's overheating, it could damage the catalytic converters, so if you replace the converter you won't fix the cause of the problem and may be back in the same boat later on down the road. If it's running at normal temps though, you ain't got nothing to worry about.

 

No matter who outputs the code it will not change.
The P0420 is the code set when the front and rear Oxyger sensor switching ratio calculations done by the computer equals 1 or greater over a programmed routine.
This is the way the cat efficiency or end of life is detected.
Question is (in hind sight) have you been running poor gas and or a lot of additives for a long time, burn oil etc.. These things kill the cats.
There is always a possibility that the sensors are bad, not heating or there is a leak of air into the system causing the cats to run cold but since it is one side, I would guess the cat may be at end of life.

 

The only additive I have ever used is rxp ...about twice yearly...was told to use this because of the reformulated gas that we have down here..this ce light might stay off foir a week or two at a time,which to me is puzzling...truck does not use any oil between changes....back in the early 90's I had a cat converter collapse on a 1985 toyota pickup; engine would not hardly run ..would not rev above 2k....pulled cat off and knocked out internals with steel rod and reinstalled ...ran just fine .I have no idea what a cat converter would cost...is it a dealer item or is there after market parts?

 

I have been told that a cat converter is either good or its bad ....it wont be bad one day or week and then all of a sudden be good for a while...what are your thoughts on this ...im leaning towards replacing o2 sensors ...the thinking was that a sensor can have intermitten trouble where as a cat converter cant....

 

Well yes. This is one of those cases where the Ox sensors are a lot cheaper than a new cat assembly so it's worth a try. You would put new ones in anyways.
Remember a couple things here in that a bad front OX sensor usually doesnot give the code you say you get.
The code you got is the results of a "computer calculation" of ratio operation between both front and rear sensors, as I stated above.

 

Looks like i have two cat converters would both need replacing? what kind of money could I be looking at?Also any way to check cat converter ...besides relying on code

 

If changing your cats, I would suggest looking 'em up online. Check out Troyer's site, they have great priced cats. Midas told me that a new cat converter would run around a whopping $600! Can you believe that!?!?!? FOR ONE!

Shop around first before you do anything, or it'll cost you more. Good luck in your findings and keep us posted.