Computer Recalibration for + or - Size Tires
#1
09-22-1999, 11:37 PM
Join Date: Mar 1999
Location: Windsor, VA
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Computer Recalibration for + or - Size Tires
For those of you who had to get the computer recalibrated, not the little mechanical speedo gear, for larger or smaller tires.....
How much did it cost and how long did it take once they started doing it?
Going to put on my 31x10.50 in a week or two and need to set aside another small fund for the computer recal.
Thanks in advance and take it easy,
Mark
How much did it cost and how long did it take once they started doing it?
Going to put on my 31x10.50 in a week or two and need to set aside another small fund for the computer recal.
Thanks in advance and take it easy,
Mark
#2
09-23-1999, 11:23 AM
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I am interested in this too. I have gone from 235/75-16 to 265/75-16 and plan on going to 285/75-16 in the near future.
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'97 F150XL 4.6L 5 spd 4x4 SC, Quicksilver Metallic,
265/75-16 Wild Spirit MPT tires on factory steel wheels, K&N air filter, Leer fiberglass topper, Access Roll-Up Cover, bug deflector, rear custom Ford mudflaps, bedliner, Pioneer Supertunner CD, 4 Cerwin Vega Speakers. Future mods: BFG's and wheels, bucket seats, shocks, duel exhaust for starters.
[This message has been edited by Michael Reschke (edited 09-23-1999).]
------------------
'97 F150XL 4.6L 5 spd 4x4 SC, Quicksilver Metallic,
265/75-16 Wild Spirit MPT tires on factory steel wheels, K&N air filter, Leer fiberglass topper, Access Roll-Up Cover, bug deflector, rear custom Ford mudflaps, bedliner, Pioneer Supertunner CD, 4 Cerwin Vega Speakers. Future mods: BFG's and wheels, bucket seats, shocks, duel exhaust for starters.
[This message has been edited by Michael Reschke (edited 09-23-1999).]
#3
10-04-1999, 10:06 PM
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#4
10-06-1999, 01:01 AM
WARNING:
The following was submitted to the 1980-96 F150 mailing list (on another site) and I can not verify its accuracy, nor do I take responsibility for anyone trying to do this.
[This message has been edited by nomo (edited 10-06-1999).]
The following was submitted to the 1980-96 F150 mailing list (on another site) and I can not verify its accuracy, nor do I take responsibility for anyone trying to do this.
Here it is. Enjoy.
Here is the BEST way to calibrate your electronic speedometer. Don't try to calculate tire size, wheel diameter, revolutions per minute etc. because this is all speculation and is subject to unknown error.
Simply drive a known distance from point A to point B and measure this using your tripmeter. You can do this by using mile markers along the freeway. The odometer and the speedometer are always related. You change one and the other will change.
Therefore, if you drive 10 miles and your odometer says you only went 8 miles,
you need to increase the conversion constant by 20 percent. The conversion constant is simply a numerical factor like 980 that will appear when your speedo is in the calibration mode as explained below. This sounds difficult but is much easier than trying to calibrate a gear driven speedo.
NOTE: The module can only be reprogrammed SIX TIMES.
Locate the dealer mode programming enable single-terminal connector. The connector is located at the bottom of the instrument
panel below the center of the glove box. On all vehicles, the dealer mode enable wire is Circuit 567(LB/Y).
Insert a jumper wire or alligator clip in service wire and clip other end to vehicle
ground with the key in the OFF position. Turn key to RUN while holding down the trip odometer RESET button on the speedometer.
Release RESET button. The Speedometer will prove out(sweep across dial and back). The English/Metric and revision levels will be displayed. The last number of the display is the dealer mode lockout count. This count
shows the number of allowable conversion constant changes remaining. When the count is zero(0), no additional changes can be made to this instrument cluster. If a revision is required a service instrument cluster must be
ordered. Press and release RESET button again and PSOM conversion constant without the decimal point will be displayed followed by the word CAL. Press and release the odometer SELECT button as many times as necessary to change the conversion constant to the correct value.
Note: Pressing and releasing the RESET button to lock in the new conversion constant reduces the number of times the PSOM can
be reprogrammed by one count. If you change your mind and want to go back to the old conversion constant, turn the key OFF BEFORE you lock in the new constant.
When the new correct value is displayed in the odometer window, press and release the RESET button to lock in the new conversion constant.
Turn the key OFF and disconnect the ground wire and check to see that the speedo works correctly.
Here is few extra tips for you.
This PSOM connector is located exactly below the glove compartment in precisely in the middle. It is a one wire connector the designation Circuit 567(LB/Y) means that the
wire is LightBlue/with a Yellow stripe.
The connector is attached to a plastic tab and has the letters PSOM stamped on it, you can't miss it. Just clip on an alligator clip with wire to the connector pin (brass tab)
and clip the other end to ground - any bolt that is attached to the metal of the body. The object here is to short that wire to ground which can be done many different ways.
The most important thing is to make your adjustment correctly. You need an accurate measurement of the distance you travel compared to your odometer. Then you can figure out what percent your speedo is off and adjust the "constant" number accordingly.
You reduce the constant when going UP in tire size. This is the direction it will naturally want to go. ie. a countdown.
You increase the constant to go to smaller tires. In order to do this (or if you overshoot your target constant number) you will have to go all the way down to about 500 or 600 (can't remember) and then it will
wrap back up to 1100 and start counting back down from there. In my case, I believe the truck was factory set at 967. I had to go down to about 880 if I remember right, or reduce the constant by about 8.9%.
It's a piece of cake - and I'm a complete idiot when it comes to fixing stuff myself. I'm learning though..... Have fun!!
Sheldon Charron,
Manitoba, Canada
P.S. You only have "six wishes", don't waste them.
Here is the BEST way to calibrate your electronic speedometer. Don't try to calculate tire size, wheel diameter, revolutions per minute etc. because this is all speculation and is subject to unknown error.
Simply drive a known distance from point A to point B and measure this using your tripmeter. You can do this by using mile markers along the freeway. The odometer and the speedometer are always related. You change one and the other will change.
Therefore, if you drive 10 miles and your odometer says you only went 8 miles,
you need to increase the conversion constant by 20 percent. The conversion constant is simply a numerical factor like 980 that will appear when your speedo is in the calibration mode as explained below. This sounds difficult but is much easier than trying to calibrate a gear driven speedo.
NOTE: The module can only be reprogrammed SIX TIMES.
Locate the dealer mode programming enable single-terminal connector. The connector is located at the bottom of the instrument
panel below the center of the glove box. On all vehicles, the dealer mode enable wire is Circuit 567(LB/Y).
Insert a jumper wire or alligator clip in service wire and clip other end to vehicle
ground with the key in the OFF position. Turn key to RUN while holding down the trip odometer RESET button on the speedometer.
Release RESET button. The Speedometer will prove out(sweep across dial and back). The English/Metric and revision levels will be displayed. The last number of the display is the dealer mode lockout count. This count
shows the number of allowable conversion constant changes remaining. When the count is zero(0), no additional changes can be made to this instrument cluster. If a revision is required a service instrument cluster must be
ordered. Press and release RESET button again and PSOM conversion constant without the decimal point will be displayed followed by the word CAL. Press and release the odometer SELECT button as many times as necessary to change the conversion constant to the correct value.
Note: Pressing and releasing the RESET button to lock in the new conversion constant reduces the number of times the PSOM can
be reprogrammed by one count. If you change your mind and want to go back to the old conversion constant, turn the key OFF BEFORE you lock in the new constant.
When the new correct value is displayed in the odometer window, press and release the RESET button to lock in the new conversion constant.
Turn the key OFF and disconnect the ground wire and check to see that the speedo works correctly.
Here is few extra tips for you.
This PSOM connector is located exactly below the glove compartment in precisely in the middle. It is a one wire connector the designation Circuit 567(LB/Y) means that the
wire is LightBlue/with a Yellow stripe.
The connector is attached to a plastic tab and has the letters PSOM stamped on it, you can't miss it. Just clip on an alligator clip with wire to the connector pin (brass tab)
and clip the other end to ground - any bolt that is attached to the metal of the body. The object here is to short that wire to ground which can be done many different ways.
The most important thing is to make your adjustment correctly. You need an accurate measurement of the distance you travel compared to your odometer. Then you can figure out what percent your speedo is off and adjust the "constant" number accordingly.
You reduce the constant when going UP in tire size. This is the direction it will naturally want to go. ie. a countdown.
You increase the constant to go to smaller tires. In order to do this (or if you overshoot your target constant number) you will have to go all the way down to about 500 or 600 (can't remember) and then it will
wrap back up to 1100 and start counting back down from there. In my case, I believe the truck was factory set at 967. I had to go down to about 880 if I remember right, or reduce the constant by about 8.9%.
It's a piece of cake - and I'm a complete idiot when it comes to fixing stuff myself. I'm learning though..... Have fun!!
Sheldon Charron,
Manitoba, Canada
P.S. You only have "six wishes", don't waste them.
#5
10-10-1999, 01:22 AM
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Location: So. Calif
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To all the above!
I replaced my tires with 305/70/16's and did not recalibrate anything. There wasn't a noticable change in gas milage nor anything else for that matter. I went through all the same questions you all did when I upgraded....finally I found a tire shop that assured me that no mods were necessary...they were right!
1999 F150XLT 4x4 Extracab Longbed; tires-Goodyear AT/S 305/70/16 (very close to a 33" tire) mounted on AR Baja's (selected for the ease of cleaning after a day in the mud)
I replaced my tires with 305/70/16's and did not recalibrate anything. There wasn't a noticable change in gas milage nor anything else for that matter. I went through all the same questions you all did when I upgraded....finally I found a tire shop that assured me that no mods were necessary...they were right!
1999 F150XLT 4x4 Extracab Longbed; tires-Goodyear AT/S 305/70/16 (very close to a 33" tire) mounted on AR Baja's (selected for the ease of cleaning after a day in the mud)
#6
08-11-2010, 11:35 AM
#7
08-11-2010, 11:40 AM
Also - do not think you have a PSOM connector ....
MGD
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#10
08-11-2010, 03:02 PM
I'll chime in the cheap mans way of fixing your speedo...
take off your gauge cluster and have a friend drive next to you on a 2 lane road (preferably closed or private) and have him yell out the window his speed...not tap your speedo needle to the correct position.
Replace glass and call it good
take off your gauge cluster and have a friend drive next to you on a 2 lane road (preferably closed or private) and have him yell out the window his speed...not tap your speedo needle to the correct position.
Replace glass and call it good
