GEN 1 speedometer reads 20mph when standing still

I was looking at a 2012 crew that was actually about everything I wanted in a truck except for one thing... I didn't notice it when I started moving, but as soon as I got up to speed I thought I was high. I was putting along and the speedo was reading 50MPH! I know the 6.2 is a hell of a lot more truck than my 4.0 ranger, but this was obviously wrong. I stopped the truck and turned it off and it still stuck at 20mph until I got moving and then it just treated 20 like it was zero and climbed from there.

I didn't drive the truck much because it stated 9mi to empty and I was on an unofficial lunch break and didn't have time to go hiking back to the car lot. I would really like to go back and check the truck out more, but the speedometer issue had me worried about electrical gremlins or trans issues. I do actually like that truck and the price wasn't bad. Does anybody have any ideas what this could be?

Thanks

I'm not 100% sure but it sounds to me like the speedometer calibration is off, possibly the previous owner used a Hypertech or tune to calibrate for larger tire diameter, or had a tune in it and it just needs an update/flash from the dealer. Is it at a Ford dealership? If so they could do that pretty easily.

Worst case it's the transmission Lead Frame but the symptoms don't really match the lead frame itself...however the speed sensors are part of the lead frame so again if it's at a Ford dealer by chance, they should be able to tell you if that TSB in the last link was done or not, and if not get it done before you (potentially) buy it. Good luck.

BenBB said:

I'm not 100% sure but it sounds to me like the speedometer calibration is off, possibly the previous owner used a Hypertech or tune to calibrate for larger tire diameter, or had a tune in it and it just needs an update/flash from the dealer. Is it at a Ford dealership? If so they could do that pretty easily.

Worst case it's the transmission Lead Frame but the symptoms don't really match the lead frame itself...however the speed sensors are part of the lead frame so again if it's at a Ford dealer by chance, they should be able to tell you if that TSB in the last link was done or not, and if not get it done before you (potentially) buy it. Good luck.

Click to expand...

I was thinking if it was calibrated for larger tires it wouldn't just sit at 20 when standing still. The truck isn't at a dealership, but I could have it taken to one if I get serious.

After looking into it more I'm not sure how I didn't notice the pictures on the listing show it idling and sitting right at 20mph so when the sales guy told me "hmm nobodies ever mentioned that before" it makes me wonder.. The guy could have just never dealt with that truck, but who knows. I was actually going to send the dealer an email calling them out on that and see what they do. If they double down on a lie then I know to run away.

Anyway, I'll take it to a dealer if I get serious about it.
Thanks