Air pressure light
 

My 08 one ton has a "check left front tire pressure light " The issue is, the tire preesure is the same on all four tires.......Help

Check your spare.

I don't think the spare is monitored. It sounds like you have a bad sending unit in the rim. I don't know what model you have but mine gives the actual pressure in each tire via the DIC. With it, it's pretty easy to see what's going on.

I worked on a 2008ish Hummer H3 a few weeks ago that had a monitor in the spare. I'd check the pressure anyways. Can't hurt, if the spare is fine, then SlimJim is right, you've got a bad sensor.