Either they both work at the same time or they don't. It would also shift very hard, the overdrive light would blink on and off when the speedo and odo didn't work. It has been going on for a couple months now. Well it finally stopped working all together and I replaced the PSOM. Now the odo works, the speedo is stuck at 85mph and I have a buzzer going off and on when I turn on the key. Any ideas???????? 1995 ford E150 5.8 engine E4OD tranny combo.

 

Update: Took van out for a 1 mile test drive, odometer working fine, speedo started bouncing around and transmission shifting fine and no blinking overdrive light. Got halfway and speedo working accurately and odo still working. Turned around and started driving back, odo stopped working, speedo still working, tranny shifting hard and overdrive light back to blinking again. Slowing down to pull onto driveway speedo stuck at 45 mph and just as I parked the speedo dropped back to zero. But still have the buzzing/beeping noise.

 

When you say the Odometer stops working are yous saying it quits updating or does it go blank?

 

Odo goes blank and speedo's needle stays on zero.

 

Drove the van again, odo and speedo work for only about a 1/2 mile. The odo goes blank and the speedo will bounce around - get stuck at highest speed currently traveled at and then just before stopping or parking it will return to zero or stop working after returning to zero. Also noticed a "stumbling" of the throttle after the other PSOM was installed.

 

Oh yeah. still has the beeping/buzzing noise too.

 

With the Odometer going blank means you either have a power/ground problem at the dash or a loose component on the PSOM board.

The beeping/buzzing also points to a power/ground problem at the dash.

 

Where would be the most likely place or location to look for a possible ground problem? I would hate to rip apart the whole dashboard to find something that might be in an easy location or totally different area.

 

We will start with the PSOM.
As you can see from the below image the ground for the PSOM is G201 & the power comes from fuse #1 and #17 of the inside fuse panel.


G201 is located:
Attached to instrument panel assembly, behind instrument cluster, see below image.


The power wiring for fuse #1 & #17.


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Going to re-install the original PSOM and see what happens. A new symptom with the current PSOM installed is no turn signals and half of the dash lights not lighting up with the headlights on. I must have gotten a bad one off Ebay.
After I get them switched, I hope I at least get something working right.

 

Will also check the G201 ground attachment.

 

You might also want to check the main body ground G101 from the NEG post of the battery.



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Original PSOM is now back in. No buzzing/beeping. Odo is working. Turn signals are working. But I am too cold to hop into it to see if the speedo is working, damn NY winters. We got 18" of snow in the last 2 days. Also no engine stumbling when I started it up and gunned the gas pedal.

 

Will check the other ground when I warm up.

 

G101 ground looks clean and tight and the speedo works. So I am believing the used PSOM I bought was junk and the original problem might have been the PSOM plugs having a bad connection behind the dash. But only time will tell. So I might be back!!!!!!