While driving to calibrate the emissions system, we first got a code for low voltage on the 02 sensor, then once that was fixed, a misfire in cylinder 5, and now that that's fixed, we once again get a code for low voltage on the 02 sensor. It doesn't seem to be lacking fuel pressure, as it will get above 4500 RPM easy, as well as above 80 MPH. We replaced all 6 spark plugs, purchased a new coil related to cylinder 5, and try our best to go through the emissions cycle properly, but it just won't happen. It's given this code at the same time as the misfire code. Any thoughts? I want to preserve my Aztek, but at this rate it's pissing me off just to hold the keys.