2006 GMC Yukon XL Denali has no voltage at the O2 Sensor. Checked the fuses and checked across the fuses and get a solid 12v. The ground wire at the plug is fine. My real question is can I just run another wire with 12v with the ignition on to the O2 sensor, or must I find and fix the break so the computer can control turning on and off the heater in the O2 sensor?

In that case you should leave it where it'* at. Either way it will not be operating as it should.

I would find the break and fix it or just leave it alone

See if it has power coming out the relay.

What relay?

The heater relay. What do you know about electrical?

Enough to be dangerous. I haven't found a wiring diagram yet for the O2 sensors. Everything I have found just talks about checking the fuses and wiring, no relay. Where is the o2 heater relay? There is not one listed in the fuse box in the engine compartment.

Thanks to everybody for your help. I believe I found the problem today. It appears that the connector on the harness side has been previously replaced. You couldn't tell by looking at the harness, but when I started pealing things back and pulled the wires out of the conduit they were spliced and the splices were a mess. I have ordered a new connector and will rewire next week. Hopefully this will take care of the problem.