Reprogramming the engine control unit (ECU) of your 1999 Ford Expedition takes two forms. The first resets the programming to factory defaults. This allows the computer to relearn the conditions the vehicle is subjected to, which is useful when new components are added. Resetting the programming also clears any adjustments made as a result of faulty parts. The second form involves a programming device. By accessing the ECU through the On-Board Diagnostics (OBD-II) port, located on the driver's side under the dash, you can modify the ECU settings to alter engine-related performance settings. Reprogramming through the OBD-II requires a hand-held reader or specialized software and equipment.
Instructions
1. Loosen the retaining bolt on the negative battery terminal. Disconnect the cable from the battery. Press the horn or brake pedal to exhaust the ECU capacitor's electrical supply. Wait five minutes and reconnect the battery cable. The ECU is now reset to the factory defaults.
2. Connect a hand-held code reader to the OBD-II port beneath the dash. Insert and turn the ignition key to electronics only mode. Turn on the hand-held programmer. Follow manufacturer's instructions to either upload a new ECU tuning file or reprogram the existing file's settings.
3. Tune your vehicle professionally. Professional tuners will connect your vehicle, through the OBD-II port, to a computer loaded with specialized software that allows custom tuning and adjusting of ECU settings. The professional tuner should retain your original ECU programming for future reference in case you need to restore the original settings.
4. Reprogram your ECU at a dealer. Dealers can reprogram your ECU, referred to as "flashing the ECU," to install the latest program available from the manufacturer. Flashing the ECU will erase all stored data and overwrite with new data. This will essentially become your vehicle's new "default" programming.
