I bought my 12 it was lifted on 35s I removed the lift put a 275 55 20 on it and I have all these lights on. Will a different tire size do this?

 

Yes having different size tires will make your ABS light come on, I have the same thing happen when I put my slicks on the back

 

All four tires are 275 55 20.

 

Four tires the same size won't set the light.
Probably damaged a sensor or harness taking the lift parts off.
Easy enough to find with a scanner.

 

I switched from stock 245/70-17 to 285/60-18 on mine and didn't set off any lights on the dash. The difference in diameter is just less than an inch, 30.5" stock vs. 31.4".

 

In my personal experiences all four tires won't set it off but gears and no tune will. Like allgonoshow said you probly damaged a sensor.

 

Whoever lifted the truck had abs wire routed all fucked up on the rear it cut it I just butt connected it. Maybe that's why. I have a scan tool but it won't read abs. Can I ohm it out at the connector or anything

 

A quivk way to see if its producing a voltage is set your dvom to alternating voltage and connect to each wire then spin the wheel. You'll get some form of alternating current. But that's so inaccurate. I'd suggest finding someone to scan the abs while on a road teat

 

When you butt connected the wires you probly added some resistance and the computer isn't seeing the signal wave form its supposed too.
Also continuity can be misleading cause a wire could be 99 percent broken but if one or two strands are still connected you'd have continuity

 

I would solder the connection. And reset codes. If that doesnt work have it scanned to find exactly wich sensor for sure and then replace.