Had same problem after a front brake job. This answer will apply to vehicles with Magnetic Wheel Sensors; Of course, always check the easy stuff first like connections, brake fluid, etc. Also, if you have access to an ABS Code reader (this reader is different than your standard code reader, and most places will charge you about $50 and up to give you a diagnosis), you may want to have that done. Anyway, I Googled for info and talked to several "brake experts." All pointed to wheel sensor problem. Nope! Not in my case. The hub of the front rotor and bearings had to be removed for the rotor to be resurfaced. In the process of removing the wheel seal off the hub (to get the bearings out), a screw driver is used to pry out this (wheel) seal. Doing so damages the seal, but it can be reinserted after straightening it out. In most cars this is o.k. But my front seals happen to have a "Tone Ring," a small thin metal band around and inside the seal. This is what the magnetic wheel senor uses to read the speed. I damaged the seals and tone ring in the process of removing them. I have a Mercedes and it only cost $7 a seal to replace. For 14 bucks that took care of it. I spent $100 on wheel sensors it didn’t even need. So if your vehicle happens to have magnetic wheel sensors, and if the rotors were removed for resurfacing, chances are the wheel seals may have been removed and caused damage to the tone rings. Other suggestions I tried that failed were: Disconnecting battery for 30 min. so it could reset, stepping on the brake & turning the steering to the left and right etc for resetting. After I replaced the new seals, I had to drive the vehicle a few hundred yards and apply the brakes a couple of times for the ABS/ESP/BAS lights to FINALLY turn off.