ABS Light

I have a 1999 Mercury Villager. The ABS light comes on sometimes. When the Light is on, it will stay on till the car is turned off. The next time the car is on, The light will be off.
Now, This is Tuesday, on Saturday, I had 2 new tires put on the car which is on the Front. I had Goodyear Reggatta's2 on them, Now I have Coopers. Also, I changed out the Motorcraft battery and put in a New Interstate Battery ( 72 Month Battery).
Can the New tires or the new Battery cause this ABS Light to come on and off? Brakes are Good. I have Appox. 20,000 more miles on the the Brakes. Is it a Sensor going bad, Bad Ground, Car speed sensor, ?????
I lost on this one. Can anyone Help.

YES the tread difference can sometimes cause a ABS problem, plus different brand tires, although are labeled the same size can be different sizes. if the ABS light has only come on after the the new tires were installed, then you should replace the rear tires with the same size, same brand.

quick test - use a tape measure to check the hieght of the front and back tires, if the difference is more then 1/4 of an inch, then its a problem (thats a guess based on the fact semitrucks have a problem with more then a 3/8" size difference)

Thank you Very Much. I will Check the tire size.