98 camaro z28 abs light on issue

I have a 98 camaro z28 automatic 5.7 ls1 with traction control. The car has sat in a heated barn for the past two years without being drove. We started it once or twice a week for the follwing years just to keep it lubricated and the battery up. now this year I planned on driving the car as a dailey driver but after installing headers i noticed that the abs light is on and there is also a little INOP light on in the lower left corner of the gauges. also the traction control switch seems like it is getting no power anymore or at least its not lighting up. Plugged a scanner into the car twice and got the same 4 codes.......

c1216 electonic brk ctrl relay coil ckt opn
c1217 electronic brk ctrl relay coil short to ground
c1244 LF channel will not move
c1246 rear channel will not move

kind of stuck right now as far as what to replace or check next. if you have any idea please respond or email me at gsbrown83@aol.com

Thanks for your time and consideration
I had a very similar problem a couple weeks ago. If it sat in a humid environment, or was exposed to a lot of moisture prior to storage, corrosion is a very likely culprit. On the bottom side of the under hood fuse box on many GM's, moisture can easily get to the connection between wires and terminals, causing the connection to rot through. Check for continuity between the terminals where they make contact with the ABS fuse/ABS relay, and the other end of the corresponding wires. Use a DVOM on the resistance setting for this, as using a test light could cause damage to the ABS module. This may not be the problem, but it's a good place to start.