Step 1: Things You Will Need
WARNING! I AM NOT A MECHANIC! I WILL NOT BE HELD RESPONSIBLE FOR ANY DAMAGES THAT YOU DO TO YOURSELF AND YOUR CAR IF YOU CHOOSE TO FOLLOW THIS!
Here is a small list of things that you will need in order to fix this problem.
Di-Electric Grease (I did not have this so I used White Lithium grease, better than nothing)
Metric socket set
Soldering Gun (optional)
Heat shrink tubing (optional)
The scanner is right, it is a bad ground connection but all of these things do not have individual sensors to tell you if it is the ground on that particular part that is bad/needs maintenance.
I had this same problem and was horrified to find out what this can cause your car to do if not fixed. Some of the things your car will do at any time while you are driving it without your doing are: Depress (or better know as STEP ON) the brakes, shut the entire car off, cause the pressure of the brakes to intensify/lessen while you are stepping on them (lets say you gently tap on the brakes, they will act as if you slammed on the brake pedal of vice/versa)
Step 3: The Fix
Put something to cover the ECU so that it does not get scratched/damaged by this.
Use the wire brush and clean the lug, and bolt, and even the bolt hole. get all of the grime off of these, all parts should look nice and shinny when you are done.
Apply Di-Electric Grease to both sides of the LUG, on the bolt, and in the bolt hole.
Apply some Di-Electric grease on top of the bolt and the remaining visible surface of the Lug all the way to the wire housing, (don't leave any metal surface uncovered)
Step 4: Optional
While the lug is unbolted heat up your soldering iron and apply some solder where with lug was crimped onto the wire were the wire is exposed on both sides of the crimp.
Put heat shrink tube over this all the way to the end of the crimp where the now soldered wire is showing.
Grease up everything and tighten the bolt back down.
This FIXED my problems. NO MORE ABS/Traction control lights! If this does not work for you try this on top of this fix
You will need some more tools for this, a Jack, and a tire Iron to remove the lug nuts of your tire. Plus wire cutters/strippers and a torque wrench and metric socket set
There has been several articles that Gm released on this harness not being assembled good and the connections that the wires are crimped to that goes into the harness have failed. A simple fix to this is to first use a scanner to find out what wheel the error code is coming form(you can just take it to a mechanic they will do this for you , it might cost or not depending on how shady they are) turning your cars wheels to the opposite side that the code is showing (if driver, turn wheel toward passenger), Turn off your car, jack effected side up, remove the tire with tire iron, disconnect the harness that goes to the ABS wheel hub, cut (MAKE SURE THAT THE HARNESS CONNECTOR THAT YOU ARE ABOUT TO CUT MATCHES THE ONE YOU ARE GOING TO SOLDER ON)and solder on the new harness connection. It is around $45 or so at Autozone, you can also check Amazon, or Rockauto for this part (you want the ABS Wheel HUB connector). put your tire back on, lower your car, torque down the Lug nuts and start your car.
This SHOULD FIX THIS PROBLEM. But if you are like me and do not fix anything until it needs to be fixed then THESE PARTS ARE 10 YEARS OLD, and might need replacing if you have not done so at all.
You can check Youtube to find a how to video on to replace the ABS hub on either side of your car if you still have this problem... I will post an Instructable on how to do this when I do so for my car.