It does not sound like a PSOM or VSS problem.
It is starting to sound more like a PCM problem. I say this because turn it off and on seems to effect the PCM more than anything else. This happens when there are bad electrolytic capacitors in the PCM.

I do not understand what the 4X4 is doing.
Need to look at some more wiring diagrams later tonight.

 

PCM that could be it.
Just before storing the truck I changed the PCM with one from Orilly because mine was burned.

When I install it, the torque converter would not disengage at stop In Drive so I could not start in D or truck would stall. I had to start in Second or first.
When I took back my truck by some magic this issue was gone but had this new issue with Odo, speedo and ABS light.

I just tested again volt between
P/O and W/P and now only 2.5 volt with ignition on. More crazy if i remove Fuse 18 I get 2.8 volt!!!
P/O and LG/B still 12.8V

Same at fuse 18 only 2.5 V

 

Next time you get that low voltage, check voltage between W/P and a known good ground. Go right to a battery - if you have to. SEEMS like your grounds are good, but this would rule it out/in.

Re. the PCM, Easy enough to test - disconnect the PCM and see if the odometer display works consistently on power-on. Remember, the PSOM feeds the PCM, not vice-versa, so even without a PCM, the PSOM should work. So if the odo displays with the PCM disconnected, and works _consistently_ (powers up every time you turn the key), but goes back to the low voltage issue with the PCM connected, then that does hint at a PCM issue.

 

Madpog
I tried with PCM unplug no change still no odo, speedo......
I tested again with fuse 18 wire with cable going to battery directly still same 2.8 Volt

 

Should I try to connect W/P wire (from fuse 18) to an other source of 12 volt?
Or is it normal to be only 2.8 Volt?

 

It should be 12V. So yeah, that would be a good test. Should light up the odo display consistently. That low voltage is the key -- SOMETHING is pulling it down.

 

I would start by replacing fuse #18.
2.8V sounds like no voltage if you use a loading test light.
These DVM's come up with voltage when there is no voltage and with no load on the circuit.
The 2.8V is more than likely coming from the PSOM.

 

So I check the fuse box diagram.

Found that fuse 15 and 18 are both fed with same 12V source at the top of the fuse.
Fuse 15 is for ABS
Fuse 18 is for Speedo, Odo, 4X4 switch

So I connect a wire from top of fuse 11 ( radio) to top of fuse 18
BINGO !!!! speedo and Odo work. Abs light 4X4 and Low range light are off.
So happy thank's to every one that helped me.

Now I have to find why those don't get any 12V

Maybe fuse J in engine bay that feed fuse 15 and 18 ( look ok) but I will change it anyway and see.

Or could it come from ignition switch that don't make the good contact? Because fuse 15 and 18 are only on when ignition on.

 

I would bet on the Ignition switch (not the tumbler).


/

 

Now that I see your diagram it's even more obvious that it must be the ignition switch.

thank you so much for all the help.
You were spot on from beginning when you said it was a power or ground problem.

 

Would you have the part number for the ignition switch? when I search I only find the barrel.

 

Is that the part that I need?
Duralast Ignition Switch LS615 - Read Reviews on Duralast #LS615

http://www.oreillyauto.com/site/c/de...2018&ppt=C0335

 

Yes that is the Ignition switch for your truck.
I hope it fixes your truck and you might have to adjust it up and down the column until every thing works.

 

what do you mean by adjusting up and down the column?

 

There are slots for the mounting screws and you need to move it in either direction to get the it to crank and so on.