Key for my 1998 expedition has stopped working.

If you hear the relay, you need to pull the door panel and check power at the motor. Power there replace it. No power, the wires tend to break in the rubber boot at the front of the door jam.

Change the horn relay and look for bad grounds. May have bad switch in steering wheel.

the electric part of the door lock is most likely going bad. you can replace it or wait until it stops working. it may keep working for a long time like that.

take the small wire off the starter solinoid and try jumping across the other two terminals with the key on. if this works the solinoid on the starter is bad.

When you start it up don't completely release the key from the crank position, let off just enough to stop the starter, if the engine continues to run the ignition switch is defective, a common problem in this year. This is not the lock cylinder but the electrical switch located down at the bottom top of the steering column that the ignition key cylinder actuates via a long steel rod.

Your key may be worn to a point that the anti-theft doesn't recognize it as the original key. If you have another key try it. Either a good locksmith or the dealer should be able to provide you with a new key. Good luck and I hope that helps..

yes it sounds like your switch and its in the steering column try these websites www.autozone.com and www.alldatadiy.com if all fail stop by your local library and get your hands on a Haynes auto repair manual for your SUV i have one for my 2000 ford Expedition and it has help me out with a lot of things wish you the best of luck Michigan Man.

Do you have a key with a resister in it? If you do then all you have to do is measure the resistance of the key and jump the wiring with the same resistance

Yes. You have to take the car to a ford dealer and have the new key programmed. This should solve your problem. Good luck.

If you want to solve your problem, click on the link I attached
Ford Expedition 1997 2002 Workshop Service Workshop repair manual Download