The other day I was firguring out my gas mileage and I was shocked a horified...10mpg. I did a complete tune up and pulled no codes I was at wits end then it hit me. The pervious owner had changed out the OEM tires in exchange for 31x10.5x15's "years ago". I checked the PSOM as per the instructions on FTE and sure enough it said 972 CAL and from what I understand that is the correct number for stock size tires. I was going to reset it and I ran into two problems...1) I could not understand the instructions on how to do it... 2) And couldn't find the rev's per minute for my tires (Yokohama Geolander H/T-S) but I assume they are close to 9.18
Can anyone help with these two problems.
1996 Ford F-150XL 4x4 5.0L 5 speed.
Manual everything and completely optionless!
I found the rev's per mile on Tirerack for your 'yokes, and it's 680. According to the FTE article about reprogramming, the new calibration constant should be 9.18.
To reprogram it, you have to ground the wiring connector under the dash, directly under the glovebox. I used a test lead with little aligator clips. While holding the reset button on the odometer, turn the key on, but not running. Press and release the reset button again to display the cal. constant, then use select to change the constant. Press and release reset one more time to lock it in. This can only be done a total of 6 times ever with your current PSOM, so do it right the first time! If you chicken out, you can shut the key off before the final press of "reset."
I found that I didn't get a good ground the first time, and it wouldn't let me change the constant.
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