Replace the o2 and go from there. Remove the negative battery cable while you replace it.

 

should I replace the one before the cat or after the cat or both? Sorry for all the questions just trying to learn and figure this thing out. Thanks, Steve

 

The code is for the one after the cat. Replace that one.

 

Pre-cat O2 won't be affected by removing the cat and it's the only one that popping a CEL will affect performance. The post cat is the one should pop a CEL after cat removal and it's the one you should put the non-foulers on, drilling out ONLY one.

A post-cat 02 CEL is only a "nuisance" light, it's letting you know that the performance of the cat is out of spec, but the PCM attempts no corrections due to it.

When I had my 2nd Gen, I went true dual (well I did weld in a simple "H" pipe just before the mufflers), omitting the cat, did the non-fouler trick and never got a CEL as long as I owned the truck...

 

Thanks alot fellas, i will replace the after cat O2. I had to hit on it awful hard to get it out. Maybe I damaged it hitting on the hex head? Thanks again..

 

You said that previously.That's why I said replace it.

 

P0037 HO2S Heater Ctrl Circ Low Bank1 Sens2

P0138 1/2 O2S Shorted To Voltage

Have you replaced that sensor? If you haven't, I think you need to. If you have, you need to have a close look at the harness for it.

 

Uhh, nevermind.

 

I will replace the O2 sensor tomorrow. will post update. Thanks again.