Why does the ABS and traction control light sometimes come on?

Check the codes, could be a wheel speed sensor, a connection problem or wiring issues. Welcome to the crazy world of Jeep.

Definitely sounds like a wheel speed sensor or wiring problem as mentioned above. The ABS computer will run a diagnosis on the ABS system with the exception of the ABS pump and modulator assembly. When you shift into gear and the vehicle starts moving the ABS computer tests the pump and modulator assembly. So if the ABS light and traction control light come on at start up and remain on it's a wheel sensor or wiring problem. But if the lights come on for a few seconds at start up then go out and stay out until the vehicle starts moving, it's the pump and modulator assembly. The ABS and traction control systems work together. So if the computer finds a problem in the ABS the traction control system is also disabled. Both lights come on to let you know both systems are disabled. Another thing to remember is the ABS computer doesn't store trouble codes. In order to get a trouble code out of the ABS computer the ABS light on the dash must be on when the computer is scanned. Shutting off the ignition will clear the ABS computer until the next time you start the engine and the ABS light comes on and stays on. Hope that helps! Jim