The data inside the speedometer(PSOM) EEPROM is corrupted and that gives the "error" in the odometer. Only fix is to replace the PSOM(speedometer). Best place would be the junkyard to find a replacement.

Bad thing is, you lost your mileage and conversion ratio that was stored inside the EEPROM.

 

 

That is totally not possible. The ONLY way to reset a PSOM is rewrite the EEPROM with good data. That involves some special home brewed hardware and software(Pony Prog) to read and write a EEPROM. That can all be found on the net.

When my 95 E350 bus PSOM(speedometer) wacked out, I was able to pull the mileage and tire ratio from the EEPROM and put it into another EEPROM and PSOM.

Here's the PSOM, the 8pin ic just left of the big flat pack IC is the EEPROM. I removed the EEPROM and put a socket in so I can swap EEPROMs out without (un)/soldering them.

 

 

Might be a bad connection on the PCB, but most likely is was a timing thing. I just lost my work shop computer just after taking the above photo! The motherboard shorted out.... bad timing.. took photo and computer shuts down!

 

ok I'll have to take it apart again and see thanks.

 

Does it say "ERROR" OR "ERROR 3" ??

Pinpoint Tests
PINPOINT TEST G: SPEEDOMETER INOPERATIVE
================================================== ==============
G3 CHECK FOR PRESENCE OF ERROR MESSAGE
================================================== ==============
Does the word "Error" appear on the odometer display?
NOTE:
"Error 3" means conversion constant must be programmed. See Diagnostic «Test F» .
Yes
REPLACE instrument cluster as described in this section. VERIFY proper operation.
No
GO to «G4».

 

I don't know if it says error or error 3 it's a truck at my work and I didn't pay to much attention to it but I think it says error 3. Well the speedo works its just hen you idle in gear it says your doing about 30 mph. And I'll have to wait till Tuesday before I can get to it since the truck is used a lot to do parts runs and is in the field all day.

 

If it says "ERROR 3" then it just needs to be programmed.

 

 

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).

-- 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. If a conversion constant change is required, a service instrument cluster must be ordered. Refer to this section for ordering information.

-- 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.

Note a 1995 F150 from the factory with factory tires (P235/75R15) would have the conversion constant set to “972CAL”.

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Before you try reprogramming, try this out 1st. Press and hold the reset button and turn on ignition(do not hook up that programming wire yet). The speedo will sweep like Subford's post above and then will show the cal and lockouts. This mode is read only so there is no way to mess up as you can't change anything. Better to check than chance changing things.

If the lock out is not "0" then try the reprogramming.