My truck is a 95 supercab XLT 2wd 5.0 40RW-70 3.31 rear end.

My speedometer/odometer quick working. It is the LCD type of odometer. My gauge cluster has the Tach. I checked all the fuses. Both under the hood and dash. I actually pulled out the fuses, looked at them, the reseated them.

I sort of checked the Vss. I followed the wiring from the VSS to the firewall. I say sort of, because I didn't hook a voltmeter to the plugs. I did however take out the VSS itself. (I was pleased to see there were no metal shavings stuck to the magnet of the VSS. Unlike the VSS on my 03 Dodge Ram with a third of the mileage!)

Right now I have the gauge removed from the dash. I have read several threads from people with the exact same problem. I forgot to mention, that when I drive the OD light blinks. It doesn't blink if I don't drive, and let it sit and idle.
The LCD on the Odometer does not display anything at all.

Now I've read about the PSOM. I'm not exactly sure what the PSOM is. Is it little circuit board sandwiched between the black gauge faces/needles and the white plastic piece that the black gauge faces are held in by? I had a hard time following others physical description of it. If it is what I described, then I didn't notice anything unusual when visually looking at it. Nothing disconnected or burned. What's a good way to check this?
On another thread, someone had mentioned that there are some people who repair the PSOM, as they are no longer sold by the stealerships. Any recommendations on someone who does this if this is the problem?

To those who solved their problem, how did you do it? On most of the threads, the OP did not come back and tell how and if they fixed the problem! (I hate it when people do this!) It seemed that some fixed it by replacing the fuse. I tried this as stated above.
Thank You in advance!

 

I just had this problem not more than a few days ago,and it had me all frustrated,turns out after buying 2 new wheel speed sensors I found that a wire had pulled out.Needless to say I was mad,but I called my local Ford dealer and talked directly to a mechanic and he said very rarely does the PSOM go bad,not saying that it won't but there is only a few things that it could be,one of them being faulty or bad wiring,a bad sensor or the gear inside the differential could have cracked or have teeth missing.I got lucky on mine and just ended up spending 50 dollars on 2 sensors i didn't need,but it beats putting in a new PSOM because that was my next option.Hope this helps and good luck.

 

Thank you! I studied the PSOM even more; and it looks like it's brand new. I was considering throwing a new VSS at it. Now that I read your post, I won't try it just yet. Thanks! I am going to quadruple check the wiring. My diff. fluid needs changing, so I'll see what I can see with the diff. cover off. I didn't think of this possibility, but I would think that the odometer/speedometer would show something. The odometer is completely blank. I might even try to run a wire straight to the gauge cluster from the VSS to see if it does anything.

 

I think you'll find that there's an issue with the power going to the PSOM, or the PSOM itself. The VSS provides a signal for the PSOM to operate, but not the power.

Good luck with the repairs!

 

I second what Bob Gervais said above.
The wiring or the VSS sensor would not cause this.
You either have no power to the PSOM or a bad PSOM.
You do not have the wheel sensors that 97FRD1TN talked about above. Sounds like he has 4 wheel ABS.

The PSOM:


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If i'm not mistaken I believe that only bronco's had 4 wheel abs 1993 and up.It does sound to me though like you have a faulty wire or connection on your PSOM,because when my speedo quit working the odometer was still lit up,it just didn't have any power back to the VSS.

 

Wheel sensors as far as I know are only in 4 wheel ABS system.
I do not know about a 1997 one ton and newer trucks like yours is why I said that above about your post.

 

Vehicle speed sensor is what is on my truck,It bolts on top of the differential,which essentially is a wheel speed sensor.

 

I essentially spent all day today on this problem! No luck so far. I started off again checking the PSOM very carefully. I looked at all the solder points with a magnifying glass. Didn't notice any bad solder points, or anything that seemed unusual. I checked the wiring. I got a wiring schematic. I inspected and jiggled the wires, and still no luck. I am convinced that I'm just not getting power to the PSOM. I was not able to check today with a multimeter. My multimeter has a blown fuse. I had a hunch that there is a grounding problem. I replaced negative battery cable from battery to the bottom of the block. It has been corroding, and based on past experience; when the negative battery cable starts corroding, the corrosion spreads to other wires. I need to get a new battery post connection. The new post connection I put on just didn't seem to make good contact on the post. I also noticed today the ground strap from the body to radiator support on the underside driver's side contact was not the best. I need to go over all grounding points.
Anyone know where to find a list of all the grounding points? In particular, the one for the PSOM. The wiring schematics I have do a bad job of showing this.
In my truck, also the intermittant wipers do not work, the wiper washer pump does not work. Also, the cruise control does not work. I'm wondering if some of these problems might be related to grounding problems.
Thank You for the suggestions so far!

 

The cruise doesn't work because the speedo is inoperative. Wiper issues are most likely the MFS (multi function switch). It's a pretty common failure item.

Get that meter goin', and check the wiring to the PSOM for power. That'll give you your answer. If there's power, you have a dead PSOM. No power, and you've got a wiring issue to figure out.

 

Here is the diagram for this system, maybe it is a better one than you have.
The ground for the PSOM is G200.
Also make sure the Body Ground is good.
The fuses are in the cab fuse panel numbers 8 & 18.


VSS/PSOM Diagram:


G200 on the Passenger side in front of the door in the kick panel:


Body Ground:


1995 Cab Fuse Panel:


Power into PSOM is on pins 1 & 3. Ground is pin #2.:


/

 

Excellent information Bill!

 

Subford

what your answer for speedometer that went crazy jump from 10-50 mph while you drive at 35 mph.

We check rear end it good. We notice if we drive on smooth road it stop jump but we have tons bad road here.

 

If you've changed the ABS/speed sensor in the axle, then it would have to be a problem with the wiring to the PSOM, or the PSOM itself.

I have the same problem, and I'm planning on checking the wiring and connectors that are shown in the schematic that Subford posted above. If everything checks OK, I'm going to get a junkyard PSOM and see if that fixes it.

 

Just did some checking and testing. I need to start off with saying that I am not that good with a multimeter. I am going to be detailed because of it.

I have the multimeter set on DCV 10.

I hooked up the red probe to pin 1, then the black probe to some metal on the dash. This is on the PSOM plug. This is the Hot in connection. The needle on the multimeter all the way to the right.
Same thing happened with pin 3 (Hot in Run.) I did have the engine running.

I next touched the black probe to Pin 2 (ground), then Pin 1 (Battery Input) to the red probe. Needle went all the way to the right.
I next did this with red probe to pin 3 (Hot in Run), then black probe to Pin 2 (ground.) Same result, needle all the way to the right.

I am guessing this is telling me that the PSOM is getting power?

I went to the junkyard, and obtained another PSOM from the same year truck. I plugged it in. Same thing (didn't work)

I next touched red probe to solder point on PSOM that corresponded with the pins above, and was getting power at the solder points. I tried touching the red probe to the various capacitors and resistors on the PSOM while touch the ground, and they all made the needle move to the right.

So now I'm really stumped. It appears PSOM is getting power; and I've used 2 different PSOMs with the same result. (I'm not ruling out that I used the multimeter wrong)

I next tried using the multimeter by touching the red probe to pins 4, 5 and 7 one at a time, and the black probe to metal on dash, then ground pin 2. The needle wouldn't move. These pins 4, 5 and 7, correspond with RABS, on pins 4,5 ; and speed output to PCM and instrument cluster. I did not test pin 9 (PSOM programming connecter) because I figured this was for the dealer programming, and I understand it only works 4 times. I didn't want to use up the usage in case I need it. I didn't really figure this would be my problem either.

So now it seems I'm getting power to the PSOM, and the ground is checking out ok. At this point I'm thinking VSS because as I posted before, the OD light starts blinking when driving. I didn't mention that on the Junkyard PSOM, the speedo/Odo is still connected to the Junkyard PSOM. I took it as a whole in case there is a problem with the LCD.

Any suggestions from here, Please? I'm guessing next step is to test continuity at the VSS. How would I do this? Another words, what setting on the multimeter, and which probe to which wire?
Again, Thank You in advance! You all have been very helpful so far!

On a good note, I obtained a wiper control module at the junkyard. I now have for the first time in 3 years (since I bought the truck) intermittant wipers, and the wiper washer works! This after testing that problem off and on for the last 3 years. Auto parts stores don't take returns, on electric parts if that wasn't my problem. I pretty much knew it was the problem, but couldn't justify spending the chunk of change they charge for a new wiper control module, and taking a small chance that it wouldn't solve the problem. The stealership wanting $200 for it. Ebay used (no guarantee $50) Junkyard $15.00, and it worked!