Possibility unrelated issue? ABS module doesn't mess with the magnasteer unless it's activated or the module goes bad, or there's a bad wheel hub seeing the whole system off.

Bad wheel hub/ module is easy to diagnose, if the light doesn't come on until after the car starts moving, bad hub. If it comes on before the car starts moving, bad module.

And if you put a non-magnasteer rack in a magnasteer car, it won't like you at all. Lots of weird stuff happens. Lol