I've calibrated the speedometer on my truck once before. Yesterday I got new tires (315/75r16) and need to do it again. I think I reached the limit (too many times adjusting it) and it wont let me change the Calibration code I've read when this happens a module needs to be replaced. Please help??? 1997 F350 4x4 5.8

 

I haven't used it, but I remember running across this device when I was looking for speedo re-calibration instructions. This may help you avoid replacing your entire cluster.

TruSpeed™ Speed Sensor Recalibrator · Superlift · www.superlift.com

 

PSOM:

linked from subford's post in this thread: https://www.ford-trucks.com/forums/1...ng-engine.html

Be aware the PSOM also contains the odometer reading. Sourcing a PSOM from another vehicle is going to invalidate your current reading.

 

Thanks! Looks like I'm shopping for a new (used) cluster.

 

If you have to replace your PSOM with a used one, and the replacement has FEWER miles than you want, you can add miles. Run your computer's sound card headphone signal out to a receiver, then the speaker outs from the receiver to the PSOM speed signal inputs. turn the volume ALL the way down, then use software to generate the square wave at the freq (about 2000 Hz). Slowly increased the receiver's volume until the needle comes up. Then I just let it run.

 

Also, you can find that informational gem and a lot more on PSOMs here:

'92-97 Speedometer (PSOM)

 

How do you adjust your speedometer?? I have 3.55 gears and recently put 285 75 r16 sized tires. Also why does my speed tach shake alot? Bad wiring?

 

Resetting the PSOM is EASY: it uses the "conversion constant" to calculate the vehicle speed from the sensor frequency. You can see yours by holding the Reset button while turning the key forward to Run, then release Reset. The needle will do a full sweep test, and the odometer display will show "E ## #", meaning English units, the microprocessor revision (mine is 08), and the conversion constant lockout count (maximum is 6). Canadian ones might show "o" in the first position meaning "Overseas" (Metric) units. Pressing Reset again shows "####CAL", which is the conversion constant (without a decimal). The constant for PSOMs in trucks originally equipped with 31x10.50's should be 9.18 . Check the original tire size on your door sticker.

If you want to change the constant, find the single-wire connector (usually marked PSOM) under the glovebox and ground the LightBlue/Yellow wire (early '92 models use a Bk/Or wire) before turning the key on (you still have to hold the Reset, as before). Everything is the same as before, except if you press Select while viewing the conversion constant, "CAL" will flash & the constant will decrease by 0.01. Press the Select button to continue decreasing the constant by 0.01 each time. (Revisions 1-3 INcrease with each press.) When the constant reaches 5.00, it goes back to 11.00 . Larger tires or fewer teeth on the tone ring require a lower constant - R&P changes have no effect. When you have the constant you want, press the Reset button to lock it in. THIS WILL DECREASE THE LOCKOUT COUNT BY 1 - WHEN IT REACHES 0, NO FURTHER CHANGES CAN BE MADE. To abort the changes and maintain the lockout count, turn the key off before pressing Reset. When finished, turn the key off and disconnect the LB/Y wire from ground. The "PSOM Programming Enable" circuit (the LB/Y wire under the dash, #24 in the diagram below) is only used when you want to change the constant and use one of the lockouts. You can check the constant without grounding that wire.

This is pulled from the link I posted above. I don't know how to put it in quotes using my phone.

 

What's a PSOM and do I "P" it?
courtesy of Steve83

 

Schwan, isn't your truck an 89'? No PSOM in it I believe.

 

You do not have a PSOM. You have a cable controlled speedometer. You need to change the gear on the cable where it goes into the trans/t-case

 

So mine says "E 08 0" it sounds like I can't calibrate anymore. Is there a way to reset it? Can a dealer or good electrical shop do it? Or am I screwed, and I have to replace the speedo cluster with a used one? If that happens, hopefully its with one that hasn't been fooled with and can be calibrated.

 

You are screwed. 6 is the most you can do. Start looking for a used cluster

 

Thanks everyone!