'95 psd A/T 145,XXX,]po\. Previous owner had rear changed, has a Jasper trans and has recent pigtail at VSS. No speedometer, odometer lights and displays but does not record. Trans shifts hard and back and forth between gears and the 'off' light flashes while driving.

I have changed the VSS and disconnected batteries several times. Using an A/E I have found no codes. Having problems and need help.
THANKS!

 

The only guess I have would be to make sure the PSOM on the back of the instrument cluster is plugged in good.

From what I hear around here if the Overdrive OFF is flashing then you have a code that needs to be read.

Check the wiring on the passenger side of transmission.

Otherwise, here is a bump for you.

Kevin

 

Will do. Again, with the A&E I find no codes.
I forgot, the ABS light stays on too.
And I have checked all fuses and power at fuses.
Thanks.

 

I do not have experience with A/E, so I can not help you there, but I thought others have said that you can pull transmission codes with it.

To get the ABS codes, you can read the procedure here:

How to: Retrieve ABS trouble codes - Ford F150 Forum - Community of Ford Truck Fans

You basically have to ground the wire they show you for the 92 and then count the flashes of the ABS light on the dash. Then take that number to find the diagnostic steps.

Do you brakes feel good, or do you have a soft pedal or a sinking pedal?

Kevin

 

This all points to the VSS and/or wiring. What brand of VSS did you install? Is it fully seated?

Did the speedometer ever work after you bought the truck? With a replacement diff (I assume that's what you mean by "rear" in post #1), I'd be tempted to remove the cover and check the tone ring.

 

The VSS I replaced was from NAPA and is seated.The rear differential was replaced prior to purchase and I put approximately 20K on truck since purchase and the speedometer/odometer has always worked. Way back when I purchased it; when switching the tanks while driving high way speeds it would occasionally go to 0 and then bounce back while causing erratic gear shifting. It has not done that for a while. The 'buzzer' for key in ignition does not work now either I can't afford to pull my hair out but this is crazy.

Also, no brake pedal problem.

 

I would try either a Ford VSS, or one from a junkyard truck. IIRC, the VSS is one of those things where you don't want to take a chance with the aftermarket.

 

We have seen faulty clusters do this because the speed signal actually gets filtered by the PSOM. We will be happy to offer a free evaluation of the cluster if you want us to test it. If it is faulty, we can rebuild it as well.

 

Mr medic, how can I isolate it to determine that it is the cluster or board or PSOM?

 

Changed a working Ford VSS from the '96 dress truck I bought new so, I know it is the OEM. and removed cluster from dash to check connections. NO change in symptoms.

I have not pulled rear cover. Will do that next.

One thing I forgot, truck has a 6 position chip, rarely used. Could this cause these problems?

 

Probably not, because the VSS directly feeds the speedo, not through the PCM. But the cardinal rule is, with any issue involving the truck's electronics, REMOVE (don't just "set to stock") any electronic mods and check again to see if the problem persists.

 

Do you have access to a scan tool that will read the vehicle speed? Depending on the tool (we have several different ones and can walk through the menus on most of the more common ones), you can read the vehicle speed from several different modules and see where the signal loss is occurring. Since the PSOM is sensing the pulses directly from the VSS, and given that the VSS has already been replaced, it's highly likely that the PSOM is the culprit though.

 

With the PSOM out, there will be no speed signal to the PCM and therefore no matter what tool the OP uses, he won't get a speed reading from a scan tool. That's exactly why there's also a shifting problem; the PCM doesn't know the vehicle speed and therefore can't shift the transmission properly.

Usually when the PSOM fails, there's also no odometer display. Also, a bad PSOM should not affect the ABS. But those are not hard and fast rules. It is a Ford electrical system, after all. Still, the more likely suspect is the wiring between the VSS and PSOM, or the VSS somehow not picking up off the tone ring.

Oh, hey wait -- to the OP, it sounds like you have another OBS truck, right? Um, well just install the cluster from that truck into this one. That'll narrow it down. You could even do vice-versa, to determine whether the PSOM in this truck is good.

 

There ain't no way I'm taking it out of the '96 dress truck, I bought that new. But, I have a '95 with the 12' bed I drive and I have a '93 factory diesel IDI parts truck. Will the instrument cluster work out of that puppy? The truck registered milage -speed etc until they pulled the engine. It was factory 4.10 and so is the subject truck. The milage is about 15K more on the '93 donor truck, I could live with that.

I have been on another unrelated project and went no further on the OBS problem truck.

 

Yeah, the speedo heads, which contain the PSOM, are interchangeable across all those. I *THINK* the calibration will be the same, because the VSS reads the reluctor / tone ring on the ring gear, and I'm pretty sure the tone ring has the same number of notches on all the 3/4-ton and up trucks. Certainly as a proof-of-concept / test, you could install the speedo from the '93 or the '95 C&C and see what happens. You could also put the speedo from this truck into the '95 C&C just to see if it works.