I have a 04 Silverado SS, which I am having a problem with B1S1 02 not reading any (mV) voltage. This is causing a rich condition which I am not happy about because it is fuel washing the cylinders in my new 408. when I initially saw this problem, I replaced both 02's with OEM 02's, to see if that was the problem. Unfortunately B1S1 still reads 0 mV. I then tested the hot and ground from the 02 plug harness. which came back at 11.8xx volts, so it seems to be getting power and ground. I guess the only thing left is the signal wire, but I don't know how to test it ?? Is there any other things i could be missing ?? Thanks for any help