Re-Calibrating the Speedometer.....effects on PCM ???
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Elder User
Joined: Dec 2003
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From: Northern California
Re-Calibrating the Speedometer.....effects on PCM ???
I found the "how to directions" for re-calibrating my speedometer and discovered that my tire size to speedometer ratio was WAAAYYYY off.
It was a simple repair/fix...after I realized what I was looking for
I test drove my truck for about 30 miles (city and hiway) afterwards and it seems to shift smoother and there might be a bit more power.
Does this re-calibration of the speedometer effect the PCM --- a/f mixture, power curve, etc.??
I know my MPG will be going up a signifigant amount now as the "old speedometer setting" was reading too slow-----I was doing about 80 mph while the speedo was reading 70 mph, hence the odometer was reading about 90 miles instead of 100 miles.
Wow an instant 10%+ gain in mpg !!!
Anyway, anyone out there know if this re-calibrating "helps" the truck as far as running better, shifting smoother, ect. ?????
Thanks,
Bob
p.s. Thanks O.I.for the idea !!!!
It was a simple repair/fix...after I realized what I was looking for
I test drove my truck for about 30 miles (city and hiway) afterwards and it seems to shift smoother and there might be a bit more power.
Does this re-calibration of the speedometer effect the PCM --- a/f mixture, power curve, etc.??
I know my MPG will be going up a signifigant amount now as the "old speedometer setting" was reading too slow-----I was doing about 80 mph while the speedo was reading 70 mph, hence the odometer was reading about 90 miles instead of 100 miles.
Wow an instant 10%+ gain in mpg !!!
Anyway, anyone out there know if this re-calibrating "helps" the truck as far as running better, shifting smoother, ect. ?????
Thanks,
Bob
p.s. Thanks O.I.for the idea !!!!
Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
I doubt it is really making the truck run better , it just seems like it because the shift points and line pressures are where they should be. It's amazing how a malfunctioning trans can make an otherwise fine engine feel like a terd.
The mileage probably hasn't changed that much, it just looks like it because your odometer shows different mileage for the same trip. You are going slower now, so it should improve a bit.
The mileage probably hasn't changed that much, it just looks like it because your odometer shows different mileage for the same trip. You are going slower now, so it should improve a bit.
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Joined: Feb 2005
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Hey Bob, how did you recalibrate your speedometer? I've got 3.73's up from 2.74's with a 31 inch tire, so the speedo reads a lil slow. Maybe I could get some horsepower back with the recalibration.
Thanks!
-Chris
Thanks!
-Chris
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Elder User
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From: Northern California
Originally Posted by Silver Streak
The mileage probably hasn't changed that much, it just looks like it because your odometer shows different mileage for the same trip. You are going slower now, so it should improve a bit.
I'm able to drive 220 miles now with a re-calibrated speedo/odometer on 20 gallons if gas......(not real #'s)
What I was getting at is the fact that I wasn't getting the true MPG figure previously when I'd check it.
I think my MPG will be up a bit now that the odometer has been corrected.
Thanks for the reply SS,
Bob
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Joined: Dec 2003
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From: Northern California
Originally Posted by cjsteak
Hey Bob, how did you recalibrate your speedometer? I've got 3.73's up from 2.74's with a 31 inch tire, so the speedo reads a lil slow. Maybe I could get some horsepower back with the recalibration.
Thanks!
-Chris
Thanks!
-Chris
It's here on this site.
Here's the link: Reclaibrating the Speedometer-----Click Here
Read the article a couple of times before you tackle it.
Look at your tire size and have the conversion constant ready.
The hardest thing I dealt with was finding the "Dealer Mode Programming Enable Single-Terminal Connector".
(It's right under the glove compartment, black, and sits sideways)
Bob
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Joined: Mar 2002
Posts: 3,545
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From: Coal Region
i just did this myself. the pcm only looks for the tire size not gearing. its based off the tire size table and constant. mine was set up for (eek) 29 in tires and im running 33s. with a well built (by me) E4OD my trck still felt like a terd and it shifted horribly. did the speedo and now it runs like a scaled dog (except for the dam low rpm miss). its a little hard to explain but the trucks shifts at 35 WOT instead of 45, which i perfer actually. and i can still bury the speedo with ease. i assumed the speedo reading was like a vacuum modulator on the C6s...since the truck has been fixed for the trans shifting it can now effectivly keep itserlf in the proper power band and rpm range...make sense? no, good!
