Use low. There are 2 wires going to each front wheel sensor, and either 2 pairs going to each rear or 1 pair of the rear axel. As with any sensor, one wire going in "high", and one wire going out "low".
Usually this is a last option, some vehicle I have seen it tripping the ABS light. GM's are usually green/wht for VSS. Post up what year, make and model of your car and see if there is a better solution.
One other thing, your car does not have Canbus, it has either class 2 data or LAN communication, which is still irrelevent to your individual wheel speed sensors. There are alot of newer GM's where there is no specific VSS, everything is read off the ABS module through data, hence using a individual wheel sensor.