Yellow Light Okay & Red Light On

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1988 Ford Pickup, 1988 Ford Cab & Chassis, 1988 Ford Bronco II, 1988 Ford Bronco, and 1987 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

Ensure parking brake is not set. If light is still on, unplug parking brake switch connector. If light goes off, replace parking brake switch.
If light is still on, go to step 3) on gasoline engine models. On models equipped with diesel engine, operate vehicle until proper vacuum is built up. If light is still on, unplug vacuum warning switch. If light goes out, replace vacuum switch. If light stays on, go to step 3).
On all models, unplug computer module connector. If light goes out, replace computer module. If light stays on, check wiring for shorts or ground.