ABS too sensitive or bad tires in snow?

If the ABS doesn't kick in very much on dry pavement, it is likely a characteristic of the tires since that's the main variable. The computer watches all the wheel speeds to see when one is a certain percentage slower than the others. A weak signal from one wheel speed sensor will make the computer think that wheel is locked up, and it will try to reduce braking to that wheel. That is different than having a break in one of the wires to that sensor. That will be detected during the continuous tests the computer runs on them. A break in the circuit will set a diagnostic fault code and turn on the yellow warning light. That will also turn the system off. The fact the light is not on and the system is operating indicates the computer thinks a wheel is turning too slowly. That is a REAL common problem on GM vehicles due to wheel bearings with as little as 15,000 miles of wear on them. For other brands, one common cause of unneeded, or "false" activation is rust buildup on the end of the sensor that reduces the signal strength to the point the computer can't read it. To find that you need a scanner that can access Anti-Lock Brake Computers so you can watch the wheel speeds and see which one is dropping out.