I have the dreaded shift/speedo change at freeway speeds.. is a PSOM something a dealer can still fix-- or do you have to send the dash out? If you get a new dash, can a dealer program it to the correct miles? (I have an EB w/digital dash)...

Thanks for the answers in advance!

 

usually failed speed sensor on top of rear differential or it's wiring/connector. corrosion or torn.

there is a thread on the Aero forum with the manual directions on DIYer programming of the PSOM. also manual step by step troubleshooting

 

From what I remember, the PSOM is a circuit on the back of the instrument panel. I don't think it is removable. But it's been several years since I changed mine.

 

I would pursue the VSS first, its failure is both more likely and cheaper to fix.

 

That's true. It's a lot easier to get to as well. I tried that first too. Didn't work for me.

 

What is the shift/speedo change? I used to have a bouncing in my green van until I unplugged the abs module.

 

it seems to shift into neutral.. and the speedo will bounce from 70 to 35 or any other random number.. one time it went from 72 to 0 then back to 72.. followed by a slight "shift" feeling

 

On mine, at low speeds (like 35) it was fine. After I got to highway speeds for a while it would start. I think the transmission kept shifting. Seems the transmission uses the signals from the PSOM to determine when to shift. So when the speedometer started bouncing back and forth, the transmission started shifting. I Changed the instrument cluster and all was well until a tree fell on it.

 

I'm with ya on this one,gents.I've got a '95 3.0 with the same symptoms.Believe it or don't,we're tracking down the problem while underway.I got pissed after the first couple times the speedo/odo went out and gave the dashboard a good whack.The transmission was downshifting randomly too.The Fonzie chop brought the cluster back on and returned the tranny to O/D. This led me to suspect a short/loose connection,so I took the dash trim off,pulled the cluster,checked the ribbon harness and connectors and reinstalled the cluster.Worked great for about a month.
Now it's back.I've got the trim off again,as well as the screws removed from both the instrument cluster and the climate control panel. I'm driving 56 highway miles round trip to work and have discovered that when it downshifts,I can actually(while my buddy holds the wheel),reach through the climate control mounting hole,snake my hand back around to the cluster, and shift between 4th and O/D by jiggling the ribbon strips.
I'm almost sure poor contact in the connectors,but cannot determine where.
Tomorrow morning,I'm giving it another shot at checking the connectors and wiring.I'll let you know what I find.Keep me posted on your progress,too and with the guys on here,we'll get em figured out soon.Thanks,David.

Edit,does anyone know if I can just swap in a junkyard cluster/PSOM,or is reprogramming required?

 

I was wondering if I bought a new dashboard (I found a place that has the digital dash new), can a ford dealer program that dash to the appropriate mileage for the van? will a new dash come with a PSOM?

 

I went to the junk yard and got the instrument panel. It has the PSOM attached on the back. I don't think it is really a separate part. You might look for a bad solder joint.

Never looked into reprogramming. I dropped about 30-40,000 miles with my swap. I just kept the number written down for when I sold it.

 

Well.. I hope I got it fixed.. the van speedometer was going crazy last weekend. Took it in to the shop and found out the speed sensor on the back axle was actually held on with zip ties! Got a new sensor and harness.. hopefully this fixes it!!

 

Crossing my fingers for you. I change mine first too but it didn't help. Of course, mine didn't have zip ties.

Let us know how it goes.