ok from my sig you will see what i have done, its a six speed if that matters. i will also add that i just rebuilt the rear with a new speed sensor and tone ring.
ok, so here is what it does, when cruising down the highway the truck will defuel around 70mph, however on my addrenaline it says the speed is ALL OVER!!! going from 95 to 110 to 106 to 123 with no pattern or reason! i dont get it and cant figure it out.

but here is the weird thing, if i unplug the speed sensor on the rear ( which makes the speedo not work) i can run the truck ***** to the wall till i redline it if i want with no defueling.

im guessing its the wiring between the rear and the pcm or the pcm itself, anyone had a problem like this or have any ideas? i miss my speedo and want the truck right again please help

 

It also could be a bad or wrong speed sensor. Or a bad setting in your pcm.

 

I have changed the sensor a few times so I know thats not it, setting in pcm ? How would I go about resetting it?

 

You could disconnect both batteries for half an hour or more, and see if that changes anything.

Any codes?

Speed sensor and tone ring OEM, or aftermarket?

 

OEM tone ring and sensor, I tried the battery trick and did nothing, I had a ecm installed 3 years ago because it wouldn't rev over 2k, now,three years later it wont let me do over 70 unless I unplug the sensor. Im leaning towards a bad pcm or maybe a reflash but idk

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OOnly codes are 1693 and 500(because I have the sensor unplugged )