The VOM meter should have been on the next higher scale but no harm done you were checking 12 VDC circuits on the 10 Volt scale.
So I would say your PSOM is more than likely OK.

Next if you can put jack stands under the rear axle with the wheels off the ground.
Put your meter on the 10 Volt AC scale.
Hook your meter to the RABS Data Connector under your hood (same as pin #4 & #5 on the PSOM plug).
Slowly increase the speed up to 30 MPH at this point if I remember right the meter should now read 6 VAC. The needle should have went up the scale smoothly with no jerks of the needle and stay at 6 VAC steady.

If this does not work then unplug the RABS Module under the glove box and try again, it could be bad. If the speedometer works now and you get the 6 VAC then the RABS module is bad.

 

The PCM is flashing the OD light because it is not getting information from the PSOM.

 

The rear wheels are off the ground. I can't identify the RABS Data Connector or the ABS Test Plug. I looked at a diagram that you posted on another thread through a search, and couldn't identify it. Is it a gray or black plug? Is it plugged in to something? Thank You again!

 

RABS Plug:


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I'm gonna have to wait a little. When I switched the neg. battery cable a couple of nights ago, the battery post connection is not that good. When my truck was idling, it idled very rough, then turned off. When I tried to restart, it made that starter ticking noise, and didn't turn over.
I hooked up a battery charger last night, and the moment I hooked up the ground, the hood light lit up. I let it trickle charge overnight. Started right up no problem this morning. It just figured I need a new battery post connector, and maybe a better battery cable.
Just went to test the RABS data connection. Had the wife sit in the seat to give it gas. when I was testing it, the truck turned off. I couldn't restart it. I have the battery charger hooked up right now. The battery is only about 6 months old.
I did before doing this test, start the truck with the RABS module unplugged to see what would happen. No change still.
I did also try to test the RABS test connector while truck was turned off. I put the red probe on each of the 2 pins one at a time. I put the block probe on the metal below the brake master cylinder. The needle moved slightly, but like I said the engine was off.

 

Worked on this issue more today. I had to improve my battery connections and grounding. I did this, and boy what a difference it made in how smooth the engine runs! It was like the old days when you can tell after doing a tune up! (Dating myself there)
I was not able to test the RABS data connection. Didn't have someone to accelerate while I use the multimeter. I ended up changing the rear diff. fluid, and checking for about the tenth time the VSS. I had read elsewhere where someone solved their Speedometer/Odometer problem by doing this. The gears in my rear diff. were in great condition, as was the fluid. I forgot to mention that I learned my truck has limited slip. I didn't know this, or I forgot. Find out while the rear wheels were raised, and I accelerated.
Also, I put everything back together on the dash to just see, If I might have fixed the problem. No luck.
This problem is annoying. I just know that it is something simple and right in front me! It has got to be a short somewhere. I'm all but convinced of this. If I'm not getting a signal from VSS to PSOM, but getting good power to the PSOM; I would think the Odometer would display something, and the Speedo would move or jump around. It is possible that both my PSOM and the junkyard PSOM are both bad. After reading other threads, It seems our trucks have issues with any kind of circuit board.

 

Do you have hitch?


that what I have trouble. I remove adapter now speedometer work like perfect. But can't tow anymore until I fix adapter for wiring harness.

 

On the above RABS plug test if you do not get anything try leaving the PSOM unplugged and with the RABS module plugged in run it up to 30 MPG and see if you get the 6VAC.
If you do you will know that the wiring to the rear end, the rear end and the RABS module are not your problem.

This is how if you take it in they will test it.

 

I just checked a 1995 Cluster with the PSOM in it on the bench and the Odometer will come on when you just put power to pins 1 & 3 and ground pin #2.
The PSOM and Cluster was not hooked to any other inputs from the VSS, RABS or PCM Computer.

 

Thank You SubFord, you are awesome! I haven't solved the problem yet. Didn't get a chance to work on it past day and a half. This info. does help me immensely. I am go to try to ground the PSOM directly from ground in the plug to some metal around dash. Next I am going to check other things such as dome lights that are connected to the same fuse. I'll disconnect them one by one to see if one of them may be causing a short.

 

Could you check plastic tube for vss sensor's wiring to front of cab?


I have issues with my speedometer it quit work and not bounce just stay 0.


Got angry and want burn this truck.

Gave 1 chance and went under truck while it soak with snow/salt. Peek in plastic tube bingo. vss wiring were ROT and cause contact together. That why speedometer go crazy.

 

I did read your other thread about, but I wasn't sure what you meant by the plastic tube. Do you mean the Conduit that is around the wiring? On my truck, It appears the wiring goes from the VSS on rear differential, along the frame, then up to the cab just in front of the firewall. Where specifically did you find the rotting? Thank You in advance!

 

It in black plastic hose.

It was rot near transmission on driver side.


It was no fun to cut 10 electric tapes from rear axle to front cab to find bad wiring.




Wire for vss I think green with stripe black wrap with red wire. Do you see that?

 

The VSS wire is green with a black stripe wire and a red with a pink stripe.
As I recall they wrapped around each other.

I re-worked the wiring diagram on page 1 of this thread so you can read it better. You might want to hit reload at the top of your screen it it has not updated.

Xclimation it sounds like you have a power problem and not wiring to the VSS or a bad VSS. If you put power on the power pins and ground the ground pin and the Odometer does not come on you have a bad PSOM, Odometer or the ribbon cable between them.

Wiring to the rear end from the dash plug C205:


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I finally had a chance to look at this problem again! Work and Rain! I don't have a garage or covered area. I found another thread where someone who had the same problem found a problem with the trailer wiring. I took a closer look at mine, and this is what I found. Any clue on where these wires might go?




www.flickr.com/photos/xclimation/4543045219/
A clue to my problem: this happened just after it snowed. I'm thinking the freezing could have accelerating wire decay.