Diagnosing ABS issue without diagnostics

The ABS has given up on my 1991 850i however the dash check light is not lit (bulb is not blown as it lights at start up). Unfortunately, I have not been able to scan the car and nor have a number of dealers and experienced BMW service agents locally. I haven't had time to try and solve the diagnostics issue but am wondering if there are some manual ways I can easily test what's wrong with the ABS. If it was the pump or control unit I'd expect the dash light to trigger... Would I be right?



I can probably get a working control unit so can test that easily but don't want to start switch pumps unless I know it's the root problem.



I know getting the diagnostics working would be ideal but isn't possible currently. Any other suggestions would be greatly appreciated.



Thanks in advance.

Diagnosing ABS issue without diagnostics