Ok long story short I ECU had been throwing codes for a knock sensor and EGRC solenoid for a while so I had to fix these before I could pass emissions, well after fighting with the dealers, realizing how inaccurate the haynes manual is, and studying diagrams I got both of those fixed. Now I'm getting a 0303 and 0503 for left and right bank front O2 sensors/circuit. What the hell... never thrown this code before... anybody have any idea how to easily test these? I'd rather not replace them (full exhaust, new KS, new EGRC SV, new valve cover gasket, I'm about tapped) and it seems odd that all of the sudden they would both go but it's thrown the code a couple of times so I know it's not just a fluke.

The only thing I can think of that could possibly send both of them out is a short. They share two leads from the PCM and the third on each harness has it's own pin on the ECU but it's the return voltage. When I pulled off one of the harnesses I noticed that it was missing that handy-dandy rubber seal that keeps moisture out, but the other still had it. Probably lost it when I was doing the y-pipe. Since then I sprayed some degreaser on the engine and rinsed it off with water, which with the one missing the jacket it could in theory short both of them out I think... and O2 sensors are supposed to be super sensitive to shorting out. But now that I have my theory does anybody know an easy way to test these? I read in the FSM that you can test them by measuring the voltage between a ground and pins 50 + 51 for the different banks, but that would be great if only I could get to it.