Well my upstream O2 sensors are not working. They are showing .1 volts. They did this when i got my car tuned last year but i just changed them the other day and they are still not reading any voltage. Where do i start looking for the gremlin? It sounds like wiring somehow but how can both be bad? Doesn't make sense? Is there a fuse for this type of thing? I'm guessing not but just hoping it might be a quick fix. How would i find out if it's a wiring problem anyway? Any other ideas?