Crazy Speedo Calibration issue. Solved!

[QC22]

I went to 35s a few weeks ago on my JLURR along with a MetalCloak 2.5 lift. Had a shop do the work. When I picked it up I used my iPhone GPS speedo App to verify the change to the speedometer that I expected. I was pleased to find that the shop had reprogrammed the Speedo. Next day, checked again and it was off the expected percentage. Observed this back and forth over a couple of days. Thought the truck was flippin' out. Was driving me nuts. Then I had my wife download a different GPS speedo App and hers was dead on, and mine was off, so I assumed it was the App. Downloaded the same one she was using, and mine was still off, hers was on, simultaneously. So now, I think it's my phone. I then manually calc'd the speed, and the vehicle speedo was definitely off the correct percentage (never reprogrammed) and then it hit me: When the iPhone is plugged into the vehicle USB port under certain conditions (time plugged in, start-up, etc) the Apps both picked up the speed from the VEHICLE, not GPS. So weird, but a warning to all. Unplugged, GPS speed is correct and vehicle is off. Plugged in, they agree and are both wrong. Literally took weeks to figure out.

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[Dan M.]

The upgrades look great. Thanks for the info, I wouldn't have figured that out.

 

[QC22]

I wouldn't have figured that out.

Was driving me bananas. So odd that the Apps revert to the vehicle for speed? Why would they do that? It's GPS.

 

[SSWIM]

I went to 35s a few weeks ago on my JLURR along with a MetalCloak 2.5 lift. Had a shop do the work. When I picked it up I used my iPhone GPS speedo App to verify the change to the speedometer that I expected. I was pleased to find that the shop had reprogrammed the Speedo. Next day, checked again and it was off the expected percentage. Observed this back and forth over a couple of days. Thought the truck was flippin' out. Was driving me nuts. Then I had my wife download a different GPS speedo App and hers was dead on, and mine was off, so I assumed it was the App. Downloaded the same one she was using, and mine was still off, hers was on, simultaneously. So now, I think it's my phone. I then manually calc'd the speed, and the vehicle speedo was definitely off the correct percentage (never reprogrammed) and then it hit me: When the iPhone is plugged into the vehicle USB port under certain conditions (time plugged in, start-up, etc) the Apps both picked up the speed from the VEHICLE, not GPS. So weird, but a warning to all. Unplugged, GPS speed is correct and vehicle is off. Plugged in, they agree and are both wrong. Literally took weeks to figure out.

Yep. Same thing on mine.

Sam

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