2002 Toyota Sienna ABS problem

Electrical problem
2002 Toyota Sienna 6 cyl Front Wheel Drive Automatic

Hi,

Recently my ABS light and brake comes on when the car is warmed up. It does not come up at a cold start. I ignored it back then and now a big problem has occurred. When I'm on the highway driving, the speedometer all of a sudden goes from the speed I'm going to zero, but the car is moving. If I were to step on the gas pedal, the car revs and it feels like I'm stuck in the first gear. The car slows down to about 15-20mph. Then if I were to turn off ignition and restart the minivan, the abs light stays on, but the speedometer works and its like it never occurred. Sometimes at warm start the tire light comes on and after a while, it automatically turns off.

When I shorted the two point in the diagnostic port, the abs light stays on, but the cruise control blinks and I read a code of 15, but can't find error code 15 in the manual.

Could it possibly be the ABS module or a speed sensor problem?

Thanks.