u1000 seat belt light will not come on air bag light is on and not flashing

Hello, you'll need a diagnostic tool capable of pulling "B" body codes. Not just P or U codes from the powertrain. I think that could be why you are not getting any relevant diagnosis trouble codes. That said, U1000 is kind of a generic lack of communication code over the CAN network. This can be caused by a simple lack of sufficient electrical voltage. So, it's really hard to know what's going on. Continued testing needs to be performed, but as said - you'll need more than a simple code reader to figure this out. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops