Brake Warning System
WARNING: This page is about a different car, the 1994 Chevrolet Lumina APV. However, it is still accessible from the selected car via links, so may be relevant.
If warning light does not glow with ignition switch on, engine off, and parking brake released, check for defective light bulb. If bulb is okay, check for open in circuit. Remove wire connector from differential pressure switch on brake combination valve. Touch connector to ground. If warning light does not glow, repair open in circuit. If light glows, circuit is okay. Replace differential pressure switch.