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Speedometer Reprogrammed by Dealer, No Change, Why?

 
Old 01-31-2019, 10:40 PM
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Default Speedometer Reprogrammed by Dealer, No Change, Why?

Greetings all! I've been searching for an answer, no luck yet. Maybe y'all can help me. I wanted to upgrade my stock 275-55-20's to 275-65-20's (31.9" to 34.1"), same width. I found a nice set of Michelin LTX AT2 pull offs for $500, mounted and balanced. That said, of course my speedo is off now (under by 5 mph @ 70). I went to the local Ford dealership to see if reprogramming was possible. The had to go by what tire sizes were available in IDS and we went with 315-70-17, which is 34.4 inches in diameter. After reprogramming, the speedo should have only been off by -0.9%. So at 70 mph, the speedo should only be -0.6 mph (nearly spot on...). So why didn't the reprogramming correct my speedo? Is there something else I should do? Or did I waste my money.....lol. I attached the printouts they gave me. Bottom sheet is before, with tire options, top sheet is after reprogramming, showing that it accepted the program...….ugh!

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Old 02-01-2019, 12:36 AM
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Well, after reading endless threads on this subject, I guess I'll need a tuner/recalibration tool, or go the [color=left=#222222]Forscan route. What a bunch of bull...… Should I go back to the dealer and have them reload the factory 275-55-20's? I am really surprised that a certified technician doesn't know diddly about the subject. Hmmm.....or maybe they play dumb and it's a way to make a quick buck?[/color]
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Old 02-01-2019, 01:45 AM
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your post doesn't surprise me in the least.
I had a dealer reprogram my 2010 & then maybe a year later my 2011.
I had changed on the 2010 from P235/70/17 to LT245/70/17....on 2011 P275./65/18 to LT275/70/17

Both trucks were reading low by 3-4 per 100 miles.....as I charge by the mile & do considerable mileage I not only want it right but I
also have to be somewhat right with sometimes 2-4 others on my trip, that also charge the same way....

Mile charges of 1500-1800 in 3-4 days
Both trucks came back reading exactly the same lower mileages....just as if they were not reprogrammed....
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Old 02-01-2019, 08:24 AM
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Originally Posted by maco View Post
your post doesn't surprise me in the least.
I had a dealer reprogram my 2010 & then maybe a year later my 2011.
I had changed on the 2010 from P235/70/17 to LT245/70/17....on 2011 P275./65/18 to LT275/70/17

Both trucks were reading low by 3-4 per 100 miles.....as I charge by the mile & do considerable mileage I not only want it right but I
also have to be somewhat right with sometimes 2-4 others on my trip, that also charge the same way....

Mile charges of 1500-1800 in 3-4 days
Both trucks came back reading exactly the same lower mileages....just as if they were not reprogrammed....
Thank you for the reply! Exactly my experience.....has anyone used the Rough Country tire programming tool? It's a little cheaper than the Hypertech….just curious.
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Old 02-01-2019, 09:18 AM
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Maybe it's because I'm a DIY kind of guy but given the reasonable cost of an OBDII compatible interface and the fact that Forscan is free, I went that route. It probably worked out to be less than what the dealer would have charged, and I knew the guy who was doing the work (ME) , LOL.

And then afterwards I still had the hardware and software to do all kinds of other changes.

You can always confirm that the change "took" by comparing your speedometer readout to a GPS reading...
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Old 02-02-2019, 04:14 PM
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Big second to what Narly1 posted, Good OBD2 readers less than $50, with a hopefully available tablet or laptop and FORScan. KM
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Old 02-19-2019, 06:48 PM
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Hypertech speedometer calibrator works great, I just recently used it.
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Old 02-20-2019, 12:41 PM
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Thanks bobn, I went with a Rough Country. I've had a hypertech before and it worked great. I thought I would save about $30 and get the Rough Country. It took about 5 reprograms to get it set correctly, but it worked.
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Old 02-22-2019, 02:15 PM
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In order to make programming changes in ForScan you have to sign up for the trial license correct?

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Old 02-22-2019, 03:12 PM
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Originally Posted by baddceo View Post
In order to make programming changes in ForScan you have to sign up for the trial license correct?
Yes. It is no cost and is issued while onsite, Real simple. KM

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