Diagnostic Aids
WARNING: This page is about a different car, the 1988 Buick Riviera and 1988 Buick Reatta. However, it is still accessible from the selected car via links, so may be relevant.
An actual low brake pressure condition would cause both the BRAKE and ANTI-LOCK lights to turn on. This flow chart addresses a condition where ONLY the BRAKE light is on. Most likely cause would be a short to ground on circuit No. 933 or a shorted pressure switch.