Speedometer Reprogrammed by Dealer, No Change, Why?
#1
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!
Last edited by medicchief; 01-31-2019 at 10:58 PM. Reason: reload photo
#2
Well, after reading endless threads on this subject, I guess I'll need a tuner/recalibration tool, or go the 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?
#3
Senior Member
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....
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....
#4
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....
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....
#5
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...
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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medicchief (02-01-2019)
#6
Senior Member
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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medicchief (02-02-2019)
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#8
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.
#10
Senior Member
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baddceo (02-22-2019)