I HAVE A 92 F-250 THAT THE SPEEDOMETER QUIT AND THE ABS LIGHT CAME ON AND THE TRANSMISSION DOES NOT SHIFT RIGHT.
460 CID AND 2 WHEEL DRIVE.
NOTE: THERE IS NO VSS ON THE SIDE OF THE E4OD TRANSMISSION.
ANY HELP WOULD BE GREATLY APPRECIATED.
THE ODOMETER IS ELECTRONIC

 

The VSS is on the rear differential housing. Speedo, trans and RABS all use its output.
Check the wiring to it including the plug connector. Could also pull the VSS and clean any oil/gunge off of it.

 

Thank you--I will keep you informed as to the results.
Thank you again very much!!!

 

LAZY K---- I changed out the VSS on the differential and did not fix the problem. What would be the next step? Is there a fuse in this circuit?
Thanks
Roger

 

Could be several things. There is a tone ring inside the diff housing that the VSS is triggered by, may have to check that the ring is intact.
However check the condition of the wires from the VSS righ up the frame rail, remember some guys finding chaffed wires on frame around the trans crossmember, I think.
The RABS module is behind the glovebox, you could try unplugging the electrical plug from it and see if you get the speedo and trans back.
It could be that you have a bad PSOM (behind instrument cluster). Enter psom in the search box for more info on that.
I don`t envy you the problem, can be a huge PITA.
Hopefully some of the real experts will give an opinion soon.
It is important that you get this sorted to protect the trans from extra hard shifts, so don`t give up on it.

 

Is it true that error codes will not show up this problem?
Also, I don't know if I mentioned this but the ABS light goes out when starting but comes on in about 15 seconds.
What a nightmare.

 

Fuel Injection Technical Library » How To Run a Self-Test Here is a link on how to check for trouble codes. However it would be unlikely you will get anything other than a VSS fault code. Code meanings from list on right.
A nightmare indeed.

 

I had the same problem a few days ago on my 97 f-250 460 and it was the fuse in the cab not the pdm a its a 30a near the top of the box if i remember right

 

Thank you for your input. I will look there today and respond with the results.
Roger

 

Well, the speedometer is still dead, the "ABS" light still on and I have changed out the VSS on the differential and have checked every fuse that was even close to the one for the odometer. I have not zeroed in on the PSOM in the instrument cluster yet.
Does anyone know of a test that could be done to isolate this problem?

One test is worth a 1000 opinions?

 

Mine was the wires for the vss were broken above the rear axle where they drop down going to the rear axle. They almost looked cut, but it was probably flex or critters.

 

Here you go:

CHECK SPEED INPUT SIGNAL TO PSOM

NOTE: Only wiring harness end of connector is to be probed.
* Connect Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to Pin 4 (speed in ) and Pin 5 (speed in -) of the PSOM connector (C252).
* Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle (driveshaft) speed increases from 0 to 48 km/h (0 to 30 mph)?
OR:
* If available, a frequency counter may be connected to Pin 4 (Speed in ) and Pin 5 (Speed in -).
* Does the displayed frequency of the signal increase smoothly and continuously from 0 to approximately 667 Hz at approximately 48 km/h (30 mph)?
OR:
* If neither a voltmeter nor frequency counter is available, vehicle speed control may be used as a good indicator. If it works normally, then the speedometer module is at least receiving a speed input signal and the wiring and sensor can be assumed to be good.

A diagram from Steve83:


Substitute RABS for the mention of the 4WABS module in the diagram. Regardless of which brake control system the truck has the VSS signal flow to the PSOM is exactly the same.


Did you disconnect the wiring to the RABS module as mentioned earlier? A very common cause of the issue you describe.


Make all checks payable to CASH

 

Not sure what the diagram above is for but it is not for any FORD truck I have seen.
That is not how the VSS to the PSOM is wired.
It is wired like the below diagram & image.

 

rla2005,
Thank you for the response.
No I did not disconnect the RABS module because I'm not sure what it looks like. I understand that it is behind the glove box? Is this a box or plug or is it marked.
If disconnecting the RABS module makes the odometer work ? then does it need to be replaced?

 

It's something I refer to from Steve83. The basic diagram is what I point an OP to looking at for the how the VSS signal gets to the PSOM. I also point out the directions for how to check the input signal to the PSOM. The diagram is for reference only and I make a note to disregard the reference to the 4WABS controller which only came on a Bronco of that era.

I apologize if you feel it is leading someone astray.

If you were still wondering, it's a PSOM diagram for a '96 Bronco. '93-95 is similar.