I got the Cat Sys Eff. Below Threshold(B1) Blues

[IgotTwo]

Well I picked up a CEL code of PO420 - Catalyst System Efficiency Below Threshold (Bank 1) - 97 X SOHC +90K mile.

I cleared the codes and a week later...... it has shown its ugly head again!

From the best I can find in prior posts, the signs are strongest to a bad "Cat."

Since we all know a "cat" is an expensive item, any suggestions of any other things that I might chase down before I go to replace it.

With 90K, and if it is the "cat," I guess swapping out the O2s would not be bad thing, if I plan to keep it.

Why do I think I'm seeing a lot of bills with General Grant's picture on it .. to get this one fixed? haha

Any thoughts?
Thanks

 

[jimbo74]

yeah... id try 02 sensors first.... if it was the cat shouldnt both bank 1 & 2 be screwed up?

 

[Texan01]

If the cat was slagging down you'd notice a gradual power loss, like not being able to maintain 70mph with out flooring it and keeping it in 2nd or 3rd all the time.

 

[RGLDan]

The O2's are not the problem here. The O2's are in front of the cat's and they monitor exhaust from the engine. The cat monitor is downstream of the cat and it monitors exhaust past the cat's. The O2's have green hardshell connectors and the cat monitors have blue hardshell connectors. When checking these sensors the O2's should switch between lean and rich (below .5 volts to above .5 volts) the cat monitor should not switch it should stay close to .5 volts. If it switching your cats are not doing thier job. I have seen this problem several times lately. If you get aftermarket cats, be careful, this code will probably return. The best thing to do is get Ford cats. Prepare yourself, they are high dollar.

 

[IgotTwo]

Thanks for the get back. At his point , I think you're right........ not the answer I wanted to hear but ...
Like I said:
Its just one of those situations where I'll have to peal off "the Grant brothers" till Ford says "Stop"
grrrrr