StilsonBoyz

I was going down the interstate this past weekend in my 1994 F150(5.0L w/auto trans) and all of a sudden the speedo went to zero and my cruise cut off.. Then after a few seconds the speedo returned to normal and I could reset my cruise, but my abs light was illuminated and the OD off light was flashing. I kept driving and a minute or so later it happened again, cruise cut off & speedo went to zero. After about 39 seconds the speedo jumped all the way to max and stayed there. The OD light stopped flashing and the abs light went off. The speedo has stayed on max ever since. All of my other gauges operate normally, the trans shifts fine, motor runs great, even the odometer is functioning correctly. I'm not really sure where to start with this problem, someone please help!!

StilsonBoyz

Also, the cruise(only when running on the interstate) will keep randomly cutting off. But after a couple seconds I can hit resume & it will return to where I had it set.

Chris_1

iTrader: (1)

VVS on the rear diff, RABS module, or very possibly the PSOM (speedometer/ Odometer).
First thing would be to pull the VSS (speed sensor) off the top of the diff and clean it, tiny iron filings can cause it to not read the tone ring on the ring gear.

StilsonBoyz

I will remove the VSS & clean. I'll let you know what I find. Thanks!

StilsonBoyz

This afternoon I removed, checked, cleaned & reinstalled the VSS.. No change.. VSS & connector looked to be in great condition. No visible corrosion or metal flaked on the magnet. Please advise on where to go from here. If you suggest the speedo module or RABS module please advise on how to check/test them. Thanks in advance!

Chris_1

iTrader: (1)

Hard to say where to go with this one. You don't have the normal symptoms of a failed psom or one that isn't getting proper signals.
But the speedometer is screwed up so that suggests a psom problem or a speedometer problem. The psom is actually a separate modular part of the speedometer. I would maybe be looking for a cluster just in case or at least for trial purposes. 94 to 95 is plug and play for your truck as I understand it. Information is a little vague out there but that seems to be a point of agreement across the board.
PSOM's are (again, apparently) interchangeable but the early ones were overly sensitive to fluctuation in the vss signal.
Just throwing random stuff out here which might be helpful.
I'd also grab the rabs module if you find a donor of the right vintage - it's kinda behind the glove box.
Another thing that comes to mind to at least try is the speedo self test thing you do before reprogramming.
If you hold the reset button on the tripmeter in while you turn the key to on (not start, just 'on' and keep it depressed and then release it) the speedometer will sweep all the way to max and back before the odometer does a display thing.
All I'm thinking there is that maybe doing that will cause the speedometer to kick out of whatever kind of a phase it seems to be stuck in. Worth a try anyway.

StilsonBoyz

Did the self check a little while ago. The speedo returned to zero but still will not read. I did it a couple of times to be sure. Two of the three times it only went to about 50 and them returned(instead of max). Also, when I did the self checks, E 08 6 www displayed on the odometer. If I install a new cluster in it, will be odometer readout change or are my miles stored in the main computer?

Chris_1

iTrader: (1)

Mileage is stored on a card attached to the back of the psom from what I can gather. It is apparently possible to change that card over, but may be simpler to find a psom with mileage close to your own.
I think you can add miles to the reading, but not subtract them.
If you find a compatible cluster (94, 95) with an operating psom, I'd suggest plugging it in and see if everything works then worry about mileage after you determine if changing the psom works.
Everything is modular and the tach and gauges are independent of the psom, so you can swap things out a little in there, I believe.