Wait Or Glow Plugs Light (Diesel)
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1991 GMC Pickup, 1991 GMC Cab & Chassis, 1991 GMC C3500 HD, 1991 Chevrolet Pickup, and 1991 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Light illuminates when ignition is turned on, showing glow plugs are warming cylinder combustion area to ease starting. When light goes out, engine is ready to be started. During cranking or after starting, light normally cycles on and off a few times, showing glow plugs are still warming cylinder.