Anybody have a 90-91 Sub/Blazer with working ABS?

[Irish1941]

Pretty sure my ABS has taken a dump on my 90 V1500 Sub. I get no noise from the valves in a hard stop or pedal vibration but I don't get a brake light error code either.
The rear were locking up before the fronts but did brakes all around, properly adjusted the rear shoes and that seems fixed.
I have just plumbed out the ABS altogether in past trucks but kinda want it to work now as this one is seeing a lot of highway with my wife & 8yr old in it.
Anybody have experience with the ABS? A way to test the valves without complete tear down on the system?
Thanks in advance.