ABS LIGHT COMES ON SPORATICALLY, BRAKES DONE, ABS OK

Inspect both the front and rear brakes. Including rotors, drums( if equipped in rear), abs sensors and wiring to the sensors, and brake pads/shoes. Also be sure to remove the calipers and look at the brake pads to check for worn out or uneven wear and replace if necessary. Hope this helps

Sometimes if your rear sensors are in the brake backing plates, you will get debris from the Emergency brake pads and this will affect the sensor count. As the wheel revolution is perceived to be different from one rear wheel to the other, the Traction Control system automatically activates and applies the brakes to make the wheel revolution match on both back wheels.

The Emergency brake linings can fall off of the shoes and create this problem. The brake pads in the front can also separate from the front discs and make the ABS warning illuminate.

Best have a Brake shop remove the rear brakes as they can be a pain to get off when the Emergency brake linings grind up.

Take it to Auto Zone or other parts store and have them run a free diagnostics scan. Then reply with the code. If no codes are present, you can start checking the front abs sensors. I dont believe there are rear sensors on these models.

keep bleeding and bleed the front as well the littlest amount of air will keep pedal spongy if the abs came on after doning brakes check the abs lines and connections up front the abs lines sometimes get banged up will doing brake job the abs sensor is the wire that runs from behind the rotor to the fire wall sometimes they get hit knocked into or damaged if wiring looks good have vehicle scanned for code .the code will make it easier to pinpoint what side-- if circuit problem--or if sensor went bad most auto stores offer scanning for free

I think you should get the Tierod ends checked. When you get a Front-end alignment, the mechanic will check them. Although you turned the front Rotors, when you start Braking the front tires can wander differently than when they freewheel.

Sometimes you can get a rust problem on the Rotors that were just made shiny. Moisture on the pads imprints a rust blotch on the Rotor and they grab at the rust until the rust wears down. Then they are ok.

When the rear Rotors were replaced check your bill and see if the Emergency brake shoes were changed. The E brakes should have been adjusted when the Rotors were replaced. The Shimmy you describe can also be the ABS working. The ABS is a pulsating Brake action.

Get your front-end checked first, then as the mechanic road tests it when the Alignment is complete, he can judge the brakes.,

ABS is anti lock braking system,which helps to stop car in various conditions.Wet/slippery etc
Sensors are located on all brakes
You need to go to your local auto electrician who will plug in scanner to locate fault

Probably want to check abs sensors on the back side of the wheels. Did you have a abs light on before the brakes where done?

Try having the dealer flush and bleed your system. It is very hard to bleed ABS systems yourself and have safe brakes that still work afterward. Bleeding non-ABS brakes yourself is easy not the same for ABS brakes. Valving, sensors and what-not require a tech and the correct equipment in my opinion. You do it wrong and you could ruin your ABS system. Do that and see if they firm up. I replaced my brake shoes/pads at the same time all new everything in back, drums/springs everything and new rotors up front. then I had the chevy dealer flush, refill and bleed system. Stiffer pedal and brakes work better. Keep in mind the brakes on 99 Tahoes are inaedequate, require new rotors often, heat up and fade/glaze pads regularly. I replace my pads long before they wear down because they glaze up and start fading early. I'll rough em up once maybe, next time, new ones. Every two brake jobs, new rotors for me. Just how it is. They will stiffen a bit and work better but they will never be awesome brakes. Just how it is on 99 and earlier Tahoes. Hope it helps. Very important to bleed correctly though. I'll bleed my 83 Toyota 4x4 myself but not the Tahoe.

There's speed sensors at each wheel. You may have got some contamination in front of one of them... sounds like the abs is trying to compensate for un equal speed at each wheel... and something may be blocking a proper read at one of the wheels...

is it the front or rear locking up? you really have to have this truck loaded (load valve under bed) before the back brakes come on and i think these are the same as my 1999 2500 where the rear is only abs, and not on the front..dumb design i know, but thats how it is...determining if its rear abs only and which axle is locking up will help pin point the problem...i put 100000 miles on my dodge since i got it in 2001 and i put 8 sets of pads on the front and just changed the rear lining and thats only because the rear wheel cylinder was leaking causing the rear brakes to lock up..