I have 99 f-150 4x4 4.6 v-8 auto trans. Put in new computer, had keys reprogramed, speedometer did not work after that, worked before. When ecm failed I pulled truck home about three miles under thirty MPH. When i drive the truck speedometer wont work after a mile or so odomoter mileage goes off od light flashes trans shifts all right driven it over 1000 miles Is it Speed sensor or cluster? Or something else? Thanks REDBOZ

 

I believe that I would check the speed sensor on the rear axle. It is cheaper than the speedo head.

Why the new computer. Have you checked for codes?

Are you getting an antilock warning? It is also controled by the speed sensor.

 

THANKS PMASLY I'll check speed sensor, no antilock warning. Old computer fried couldn't connect with my code reader, New computer no codes. REDBOZ

 

I just bought a 2002 F250 7.3L that is doing that same exact thing. Did anyone ever figure out what the issue was? When I stop, turn the engine off, then restart, it seems to go away????

Please let me know-
Also, when I turn on my wipers or headlights, my radio goes silent for a couple of seconds.... any ideas?

Any help is appreciated..

 

I am afraid to say(call the dealer to make sure) but I think you are going to have to go to the dealer to get it fixed. The speedo/cluster unit communicates with the engine computer and some other things over a communication network. They have to plug their little gizmo in and do some hocus pocus to get all the modules talking together again.

 

IT sounds like the GEM unit is not working correctly. This gadjet is what lets all the modules talk to each other. The only cure is a stealership. Just don't let them apply the '03 updates to your '02. It does something screwy to the engine senosrs and kills the power band.