Working on 95' F250....Trying to calibrate my speedometer...get into the PSOM screen where it displays 979 but when I hit the button to do the countdown to the value I need nothing happens. PSOM value won't change. It has a good ground, I verified that...and speedometer/odometer work so wouldn't suspect any issues with the module on the gauge cluster itself. And the reset and other button themselves work fine, I have no problem restting my trip etc. Any ideas!? Thank you!

 

From what I recall, PSOM can only be recalibrated 3 times, ever. Maybe it has been recalibrated before.

 

You can do it up to 6 times and when you enter the screen it will let you know how many times it has already been recalibrated. This truck has never been recalibrated before.

 

Reprogram speed conversion constant using the following procedure:
-- 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) or 571 (BK/O) for early 1992.

-- Insert metal clip in service wire panel connector. Clip other end to vehicle ground while the key is in the OFF position.

-- Turn key to RUN (not crank) position while holding down the trip odometer RESET button on speedometer.
Release RESET button.

-- 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 programming 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.

-- Press and release RESET button again and PSOM conversion constant (without the decimal point) followed by the word CAL.

-- Press and release the odometer SELECT button as many times as necessary to change 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.
The module can only be reprogrammed six times.
If you change your mind and want to go back to the old conversion constant, turn the ignition switch off before you lock in the new constant.

-- When the correct new value is displayed in odometer window, press and release the RESET button to lock in the new conversion constant.

-- Turn the key off and remove the ground wire. Verify proper speedometer operation.

 

I know what the process is. The display will not change when I hit the button to start the countdown...THAT'S the issue I need help with.

 

As I recall, you can only do this process a limited number of times, and then the PSOM will no longer allow changes. It's entirely possible that yours has hit the reprogramming limit.

 

Please read above comments, you are allowed up to 6 this truck has never been changed before.

 

What number does the psom display for number of changes remaining? Your statement about it telling you how many changes have been made, isn't quite right. It tells you how many changes are left. If it displays zero, it's locked out, cannot be changed again. If it displays 6, then you are correct and it has not been changed before.

If it does display six (or anything but zero), I've never heard of this problem before, so unfortunately I don't have anything helpful to add.

 

Correct and it displays 6...i've done this many times before and never had this issue...thatscwhy i posted, see if anyone else ever experienced this. Thanks.

 

having the same problem you are with the calibration not counting down we’re you able to figure it out?

 

Yes. I was grounding the PSOM to my truck seat frame as I always do. Apparently this doesn't always work. Run a longer ground directly to the TRUCK FRAME and you should be good.
Check out REDNECK TECH on youtube...lots of good OBS vids from fixing a loose/wobbly steering wheel to installing 7.3 Turbo Downpipe and EGR system overview with more always being posted.

 

yeah i didn’t have a good enough ground ended up finding a ground strap on the frame just hooked it up and it let me calibrate it thanks!