I have an 03 f150 5.4, it runs fine, shifts fine and will get up to speed. I can go over 40 but the speedo will only work until i get to 40 and then it just stays there. My rpm guage seems to be working fine. ------i thought it might be the speed sensor/output sensor on the trans but it shifts fine so i dunno anymore.....???

 

Do a search for "f150 hec"
There is a test that can be done via the odometer
Good luck and keep us posted

 

Found one for you, post #2
https://www.ford-trucks.com/forums/1...-use-them.html

I think the procedure is the same from 1999-2003
Maybe someone else can confirm this

 

I tried doing that test already but the only thing that happens is it clicks over from the mileage to....Txx....such as T 54.7 dunno what that means but that is what it does. i assume its tied into the mileage cuz it continually goes up.--------unless im doing something wrong.

i bought a speed sensor or it might have another name....it goes on the tail end of the trans. I hesitated putting it on cuz the symptoms didnt quite seem all there. I will try it and post back, good or bad.

 

I am not sure but I think the sensor you are about to change
is for shift points
I believe the speedo gets it signal from the one on the differential
Best to do some more research before changing parts

 

When you access the HEC test, the speedo and tach make a full sweep as their test of display ability.
Does the speedo make the sweep?
If no it has an issue or the electronics has a problem independent of any outside sensor or signal.
Good luck.

 

If the odo. says T 54.7 then keeps going up as you drive. T means trip the numbers are the mileage traveled since it had been reset.

 

I don't think you are doing the test correctly

 

Upon reading, the instructions say to turn the key
to the "run" position, it does not say to start the engine