1991 E350 with 5.8L and E4OD, 195K miles. Recently rebuilt transmission. About 600 miles after rebuild of transmission I started to get periodic erratic shifting (into neutral at hwy speed, 3rd gear at slow speed, etc). Pulling error codes after a short drive always reports 452, VSS error. BTW, I also have EGR errors (327, 328), and have a new EGR valve waiting to be installed.

I've replaced the VSS, the plug to the VSS, and tested the wiring from the VSS to the ECU as per the factory engine diagnostic manual--all tests good. I can hook a voltmeter to the VSS contact at the speed control unit (under the dash--wiring diagram shows a direct contact to the actual VSS), and I get a very steady voltage rising with speed.

I don't think the VSS error is a problem with the VSS or wiring at all. This 1991 model predates the PSOM, which apparently causes this kind of problem in later Ford vehicles (1992+). At this point I'm stumped.

Does anybody know how the ECU confirms accurate VSS data (and thus would report a VSS error even if the VSS is working)? What other sensors should I be considering here?!

thanks for any help...

 

Here's a very good write up, maybe it'll help you figure it out.
https://www.ford-trucks.com/forums/9...d-i-found.html