Well it must have been the fuse. I don't get the p0135 codes any more. So the O2's must be working. Now I get a P0171 and P0174 System too Lean Bank error. Any ideas?
If both banks are lean then it is a system issue not O2.
Most common cause for those codes coming up together is MAF sensor and/or MAF air plenum leak(big tube from MAF to intake).
MAF sensor air flow sets the "0" for fuel trim, computer bases 14:1, air:fuel ratio, on that 0.
If O2 reports too little oxygen(rich) computer reduces fuel, -1
If O2 reports too much oxygen(lean) computer adds fuel, +1
If computer gets up to +20 it will set Lean code, this is to notify driver that something is wrong, computer is having to add too much fuel IF(big if) MAF sensor data is correct.
The IF is what you need to check.
Dirty MAF will under report the air coming in, so 0 is to low which is why computer has to add what it thinks is too much fuel.
Air leak in plenum or a vacuum leak is the same thing, all the air coming into the engine must go thru the MAF or computer will set the wrong 0
Now on the other side of that equation is fuel
Computer expects fuel pressure to be with in a specific range, it has no fuel pressure monitor.
If fuel pressure is low............then computer has to increase the "+" number to get enough fuel, when it gets to +20, lean code is set.
As you may have realized "Lean" or "Rich" doesn't always mean what is says, at +20 the engine may be running fine, or even -20, what it means is that computer is seeing a problem and letting you know.
+20 is not specific, it might set code if lower or higher, it is a software calculation.