Having a seemingly strange issue with the PSOM in my truck (96 7.3, e4od). What is happening is that the VSS signal going to the PCM will occasionally drop out, leading to very harsh shifting and flashing TCIL light. I have forscan on my phone, so I am able to see the live data and have verified that it is the speed signal that is cutting out. My speedometer/odometer never have any issues, it's only the signal going to the PCM that seems to have issues.

Through observation, I have found that the issue seems to be temperature/humidity related somehow. Just to illustrate, yesterday it was a clear sunny day and I had no issues at all, but this morning it was pissing rain and cool, and I had 0 speed signal to the PCM until I started getting heat in the cab. Once things warmed up the VSS signal started popping in and out, and after several minutes it came in full and never gave me any issues. I've noticed this behaviour is really consistent, no VSS when cold, but signal returns once can warms up.

Had anyone else ever experienced this? Does anyone know of potential fix beyond just replacing the whole PSOM? Thanks.

 

Heat issues can be fun to find.
Might be able to use a hair drier to find the spot that needs the heat

 

Could be a leaky electrolytic cap or corroded solder joint in the PSOM.
PCBs are usually coated both sides, but still it could be an age issue.

 

That was my thought as well. I've had the board out and inspected it as best I could with a high quality multimeter but I couldn't find or see anything telling. There's a local guy I've used before who does cluster repair, should I just ask him to replace the caps and check the solder joints regardless of if he can find anything?

 

If your local guy can do SMT soldering, do a PSOM repair kit. It includes much more than just caps. SMT requires more than a simple pencil soldering iron.
Do a search here for a recent thread about PSOM repairs. Goggle Ford PSOM repair kits.
There's Youtube video out there about this PSOM.