GM-GMC: 1999 GMC Sierra -- ABS and Brake Light, gmc sierra, salvage yard

Question
I have a 1999 GMC Sierra Ext-Cab.  My ABS light and Brake light comes on on occasion.  The diagnosis was that the ABS module (?) was out.  If I need to replace (very expensive) can I get one from a salvage yard and what make and models will work on the truck?  Also, where is this module located and how would I get the lights to not come on?

Answer
You are correct that module is very expensive.  The module is mounted on top of the valve pack assembly on the frame rail.  Approximately under the drivers seat, or back slightly.  It is easy to recognize, it has all kinds of brake lines running in and out of it.  As far as interchaging modules, a salvage yard would best answer that question for you, however, I would guess that any 1999-2003 or so would fit.  Be aware that they can be very difficult to remove, the very small torx head bolts often strip and the heads need to be ground off to in order to remove the module.  The module is much easier to remove or seperate from the valve pack off of the truck, but that too it troublesome.  Often the lines are seized into the valve pack and once the valve pack is removed the entire braking system needs to be bled to remove air.  It is best if the module is seperated from the valve pack 'in the truck' to avoid that.
Check one thing before you try anything else.  Roll underneith and locate the module/valve pack.  There will be two wires, a red and a black wire that come out of the module and plug into the motor on the valve pack.  Look very closely at the wires.  They often corrode or break.  You may be able to simply have the wire repaired if it's location allows for it.

Hope this helps.