Can anyone tell me the size of tire my speedo is cal'd for? When I got into the codes (following procedure elsewhere on this board) I came up with "E 08 06" Which tells me that the cal has never been done after factory setting (still have 06 cals remaining). Then when I call up the current cal I get "972CAL".
According to my calculations, that is for approximately a 31" tire. Can anyone confirm that? This doesn't make much sense, since the stock tire is NOT a 31" tire.

 

972 is the calibration constant listed for P237/75R15XL all season tires which turn 720 revs per mile, the stock tire.

 

Hmmmm....okay, would you happen to know the calibration constant for 31x10.50?

 

Hi
sounds like the same problem I am having.
Could you tell me where you found out how to get these codes?


I was going to increase my tire size from 145/R75/16 (stock)
to 265/R75/16 and was told that all I needed to do was to change the VSS gear. My local Ford store is of no help.. They say they have no gear listing for a 265 16 tire. Can anyone give me specific information about this. Part#s, pnone #s, or web sites??

1998, 4x4 250 light duty, 4.6

Regards,
David

 

 

Do a search on this board for "speedo" and the procedure I used is in one of the posts (actually 3 or 4) that comes up in the search results.

'93F150 XLT 2WD Supercab
5.0, AOD, K&N, Gibson
And SOON to be Superchipped!!!!

 

Here ya go 250...I cut and pasted for ya. I'm not sure it is the same procedure for your truck.

Just one word of caution the module can only be programmed 6 times

1. 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).

2. Insert a jumper wire or alligator clip in service wire and clip other end to vehicle ground with the key in the OFF position.

3. Turn key to RUN while holding down the trip odometer RESET button on the speedometer.

4. 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 id 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 revisionis required a service instrument cluster must be ordered.

5. Press and release RESET button again and PSOM conversion constant without the decimal point will be displayed followed by the word CAL.

6. The new conversion constant necessary to correct the speedometer can be found by determining the current percentage error. One way to do this is by comparing the indicated miles versus mile markers on an interstate trip. The longer the trip, the better indication of the error since interstate mile markers are not always exactly 1 mile but the average is very close to 1 mile. Going to taller tires (indicated miles less than true miles) will mean the conversion constant must be reduced by the same percentage as the speedometer error and going to smaller tires (or a numerically higher rear end ratio) means the conversion constant must be increased.

7. Press and release the odometer SELECT button as many times as necessary to change the conversion constant to the correct value. The constant will only increase (not decrease) when the SELECT button is pressed so reducing the constant means counting up until the constant jumps to the bottom of the scale and begins counting up from there.

8. 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.

9. Turn the key OFF and disconnect the ground wire and check to see that the speedo works correctly.

 

[font size="1" color="#FF0000"]LAST EDITED ON 05-Oct-01 AT 12:51 PM (EST)[/font][p]The calibration constant for a 31-10.50R15/C A/T tire @ 680 revs/mile is 918. Data is on page 13-01-45 of my 96 shop manual.

 

Thanks for your help StrangeRanger