ABS Fails: Why Anti-Lock Brakes Don't Work

Hello everyone.

I'm the proud owner of a 1996 III-generation GTI TDI, and I'm experiencing the following problem.
The ABS is inactive (although the warning light is not illuminated). Strangely, it works when reversing. I've already used the search function, but I haven't found anything similar. I would be grateful for any tips.

Thank you.

Do the wheels lock up completely during a full stop from forward motion?

Has the error memory been read yet?