Co281 on chevy trailblazer - 1999 Chevrolet Silverado 1500

SOURCE: abs codes co281 & co265

the first of the two codes is for the brake light switch, the one that is under the dash attached to the brake rod and brake peddle. Not much to diag on that one, if its bad it's bad, and when it sets the code that means it's bad.
The second one is for the abs modual, it's under the truck on the drivers side. It is bolted to the top of the thing that has all of the brake lines going to it. MOST all of the time that code is set the modual is bad. It can be a little hard to get the bolts out they are torqs 20 or 25(i'm getting old). There are four of them holding down the modual. There are also a couple of connectors going to it. And some of the time it will blow the fuse for the abs under the hood(its in the underhood fues block). Make sure to clean off the modual before you pull it out. You don't want dirt getting in the solinoids for the BPMV(that's the thing it's bolted to).