2002 Tahoe, 4x4. 208k miles. Randomly the ABS and BRAKE lights will illuminate, usually after hitting a large hole or some other jolt to the body. I've heard a rumor that the rear module has a ground that likes to lose contact somewhere.... anyone know the veracity of this? ABS still activates, brakes work as designed even after they come on so other than being annoying to look at they are not causing any actual issues. Cycling hte key makes them go back off until the next random jolt makes them come on.
We almost bought a 'Hoe in 06 when we bought our Sierra. Kinda wish we had. This thing is a beast.
It does sound like a ground issue. There is one behind the drivers front tire attached to frame body mount, on the back side (facing rearward), it is known to cause many issues with electronics.
Another issue is the connectors themselves, they tend to loosen up over time, usually requiring replacement of the connector. Probably why the connectors are readily available online.
My rover does this every once in a while, there's a connector over the rear diff that comes apart for a split second and causes the fault. I taped mine up and it happens less often
Could be grounding. Could also be the solder joints in the ABS module. That's what it was with my brother's GMC. A little soldering kung fu on it and all was well. This guy walks through the fix pretty well...
https://www.bing.com/videos/search?q=2002+tahoe+abs++repair&view=detail&mid=B429BF8420791D8B8F22B429BF8420791D8B8F22&FORM=VIRE
See, y'all are enablers. you're enabling me to be lazy and not use google.
In reply to grover :
"less often". That should be a motto around here. I honestly wish I could take a year out of my life to learn electrical gremlins. 
Does it store any codes? That might aim you at an almost broken wire at one of the front wheels, or a worn, loose front hub bearing that for some weird reason doesn't make noise on GM trucks.
+1 on the hub wiring. While you are in there snooping around, check your brake's rear hard lines , and your front brake, and crossover lines. They like to rot on this platform.
I'm too lazy to read the question but yet inclined to reply.
A. You need to connect a scantool to see what is up. Guessing and throwing parts at it is more expensive.
B. The chassis ground on GM trucks is a known weak point but when it fails to the point that the ABS system hiccups, you also generally lose fuel pump and the driver goes into shoeleather mode. All the same, find the braided (!) ground strap from the frame to engine, which should be attached to the A/C compressor/idler arm area, and give it a tug. If it rains green dust or breaks entirely, ground the engine to the frame with a better strap. If it broke entirely, use a different vehicle to go to the parts store because now the fuel pump isn't going to work. GM grounded the fuel pump to the frame and the only metallic connection between the frame and battery is the corrosion-prone ground strap that you just broke. Driver is now in shoeleather mode (AKA walking)
In reply to Dirtydog :
lines are good shape. left rear caliper siezed up a few weeks back and we already changed it. Checked and bled the right side at the same time.
In reply to Streetwiseguy :
My scan tool doesn't read ABS codes. What makes it odd, if it was storing a code or three wouldn't the lights stay on after a restart? you can literally cycle the key at a stop sign and they go away.
