Yellow Light Stays On & Red Light Off
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.
- Apply parking brake to ensure Red light is operative. Temporarily ground diagnostic lead. If trouble code appears, go to appropriate code. If no trouble code appears, disconnect computer module. Check for voltage between terminal No. 1 on connector and ground.
- If there is no voltage, check 20-amp fuse. If fuse is okay, check power lead from fuse block to computer module. If there is 11-13 volts, check master cylinder switch. Ensure connector is plugged in. If light is still on, unplug connector. If light is still on with connector unplugged, check resistance between terminal No. 12 and ground on connector.
- If resistance is less than 100,000 ohms, repair ground wire to computer module. Ensure there is no loose or dirty terminals. If resistance is 100,000 ohms or more, plug in computer module connector. Turn ignition switch to "RUN" position. Check voltage at Purple and White wires at master cylinder switch with connector plugged in.
- If voltage is 8-13 volts, unplug computer module connector. Check for voltage between terminal No. 2 and ground. Turn ignition on. If voltage is below 8 volts or above 13 volts, check for open wire between computer module and master cylinder switch. If voltage is 8-13 volts, replace computer module.
- If in step 4), voltage was 7 or less volts, connect a test light to positive battery post and to Purple and White wire which had low voltage reading at master cylinder connector. Turn ignition on. If Yellow light goes off and test lights comes on, check for contaminated master cylinder switch terminals or defective switch. If Yellow light and test light does not come on, replace isolator diode.