Quick history, trying to help my niece get a 93 F150 4x4 with the 5.8 so she can have a daily driver. Truck has sat in a field the last 2 years. Truck was parked due to a bad starter.

Replaced starter and did all of the normal maint to get it up and running. Air filter, oil change, trans filter (just changed the filter, did not flush). Truck runs awesome, but was dropping out of OD into a false neutral and a consistent basis. Pulled codes and got a KOEO code of trans not in park and a CM codes of a MLPS voltage out of range and 452 VSS error. Replaced with a new updated MLPS and verified the alignment by pulling the OHM's at the PCM plug to ensure correct range. Cleared the codes.

Current codes are KOEO 111 (clear) and CM 452 (VSS signal). I've cleaned the VSS and then replaced it with a new VSS when the code remained.

Although the false neutral has improved, it still happens pretty regularly. I'm looking for some guidance on where to go from here. If I turn the OD switch off the trans shifts correctly and is not in limp mode. I can also get the truck up to speed and turn the OD on and it will hold until the trans needs to downshift and then it will go into a false neutral. Any thoughts?

 

The vss signal goes threw the abs module behind the glove box could be that at one point in my 96 I has a bouncing speedo unplugrd the abs module and problem solved I all so had a vsd code and a new vss

 

The speedo is solid, but if I disconnect the ABS would that possibly correct the false neutral. I really don't care if the ABS works... just trying to not throw any more parts at it than necessary.

 

On my 96 unplugging solved my vss issue the module was bad, iv seen bad computers do some crazy things I'd give it a try just cuz its that easy then check for the code after, also don't buy a cheap Napa vss go right to Ford iv seen a lot a bad vss form the parts houses around here

 

When you say you cleaned the VSS, you mean you removed it and cleaned it and the connecting plug?

 

Correct. pulled the sensor out of the rearend. Cleaned the sensor and the cleaned the plug. Then put dielectric grease into the plug and re-installed the harness. Cleared the codes and took for a test drive. It was still false neutraling and code came back. Replaced with a new Autozone part (I know, but it was worth 12 bucks to try).

 

https://www.ford-trucks.com/forums/1...l#post15016162

 

I agree, but figured it was worth the 12 bucks to try. Is there anyway to test the old VSS out of the truck, or is the only way to test is to re-install, unlug the harness, jack up the tires, put in drive and check voltage as the tire are spinning 35 mph?

 

yeah, it's a pick up type sensor so there's a gear in the diff that is next to the VSS and the VSS registers once per rev. I'm pretty certain the VSS goes directly to the PCM. And items like the speedo/trip/odometer and ABS feed from that.

 

Ya, that's what I'm trying to find out. I've been told the VSS signal goes from the sensor->ABS Module->PSOM->PCM, but I'm trying to find out for sure. I can start tracing the wires back from the VSS to see if I can find a pinched wire, but I would rather see if I can pinpoint it a little better. The cruise control works and I don't have an ABS light on if that helps. I've taken it to 3 transmission shops and they all say the transmission is shot. I really don't think its internal and i was wondering about the selinoid pack, but I figured I would get an DTC.

 

Your correct with the vss signal path to my knowledge and findings. So if the abs module is bad or the psom in the cluster is bad the trans will see no vss input and go into limp mode and do crazy things.

 

only if the psom is bad

 

The Vss does not go through the abs module, it T's off and feeds both the abs and psom at the same time, if your speedo is solid then the output of the psom or ecm is bad, you can unplug the abs to diagnose if it's bad but only if the psom isn't working

 

Since I have a certain vantage point, I took a quick look and the VSS follows the same route as the fuel line into the firewall (second paragraph - https://www.ford-trucks.com/forums/1...l#post15016367) and from there it goes directly out of the firewall to the large 84 pin connector and to the PCM. If you need to remove the 84 pin or the smaller connector, be careful, they can be difficult to get back together just due to how they are designed. I had trouble with the larger connector.

 

ok... I'll pull the ABS just to see if anything changes. Does the PSOM control the oil pressure guage at all? The oil pressure guage does not work, but I figured it was a bad sending unit and I have an external guage hooked up. Is there a way to test the PSOM to measure the output signal?