False Neutral and VSS issue
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
Okay, picture this:
VSS ----> PSOM ----> PCM
|
|----> RABS
That's how the signal path is laid out. So if the RABS controller is flaky then it can mess with the raw data coming from the VSS, which causes the PSOM and PCM to get fed bad data. That's why it's suggested to unplug it.
VSS ----> PSOM ----> PCM
|
|----> RABS
That's how the signal path is laid out. So if the RABS controller is flaky then it can mess with the raw data coming from the VSS, which causes the PSOM and PCM to get fed bad data. That's why it's suggested to unplug it.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Okay, picture this:
VSS ----> PSOM ----> PCM
|
|----> RABS
That's how the signal path is laid out. So if the RABS controller is flaky then it can mess with the raw data coming from the VSS, which causes the PSOM and PCM to get fed bad data. That's why it's suggested to unplug it.
VSS ----> PSOM ----> PCM
|
|----> RABS
That's how the signal path is laid out. So if the RABS controller is flaky then it can mess with the raw data coming from the VSS, which causes the PSOM and PCM to get fed bad data. That's why it's suggested to unplug it.
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
Perfect!!! just what I was looking for. I should also be able to isolate the different modules using jumpers as well as narrow down what sections of the harness may have issues. It'll be a couple of days until I can go test it. I will report back with results. Thanks!!!
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
Alright, pulled the RABS plug off. Cleaned the Speed Control Amplifier plug, main harness from the firewall and the PCM connector. Re-installed with dielectric grease. Still going into a false neutral when the OD tries to either engage or disengage. Did a KOER test and got 111. KOEO 111....CM 452 still. Going to pull the PSOM next and see what I find. All the wiring and harnesses look good, is there anyway of testing the PSOM out of the truck before I go to the junk yard tomorrow?
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
Sounds like a 4X4 with a two wheel filter in the E4OD causing the going into a false neutral when the OD tries to either engage or disengage.
Try unplugging the speed control module and see if that fixes the VSS problem.
Try unplugging the speed control module and see if that fixes the VSS problem.
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
According to my brother the truck shifted correctly before he parked it and the filter I put in was exactly like the one I pulled out. I still have the box so I'll go pull the part number to ensure to insure it was for a 4x4. I'll put everything back together and unplug the speed controller and report back. Thanks for all the help!!
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
Ok, replaced PSOM with one from the junk yard and unplugged the speed control amplifier. Still getting false neutral. Rechecked trans filter and it is the one for a 4x4. Trans fluid level is good. Still have 111 KOEO...452 CM... 111 KOER. Whats next?
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
Put a scope on the VSS signal from the speed control area and see if you are getting a good signal. if so after clearing the codes replace the computer.
The correct PSOM vehicle speed signal to the PCM is an AC square wave
that rises to 5 volts positive and drops back to 3 volts negative,
with a frequency of about 120 Hz at 60 mph.
This pdf shows the wave form pn pg#10.
http://www.atraonline.com/gears/2007...2007_01_04.pdf
/
The correct PSOM vehicle speed signal to the PCM is an AC square wave
that rises to 5 volts positive and drops back to 3 volts negative,
with a frequency of about 120 Hz at 60 mph.
This pdf shows the wave form pn pg#10.
http://www.atraonline.com/gears/2007...2007_01_04.pdf
/
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
I've got an old sun engine scope that I might be able to make work. I removed the heat shield and cleaned the connector for the shift solenoids and it made a drastic improvement. It still false neutraled on me a couple of times, but it wasn't constant like it was before.
I'm wondering if I need to replace that connector and about a foot of wire as I know they can go bad. I didn't see any bare wires at the connector, but I also didn't go up into the wireloom. I know it has nothing to do with the VSS issue, but I'm wondering if it could be causing my false neutral issue.
I'm wondering if I need to replace that connector and about a foot of wire as I know they can go bad. I didn't see any bare wires at the connector, but I also didn't go up into the wireloom. I know it has nothing to do with the VSS issue, but I'm wondering if it could be causing my false neutral issue.
Thread Starter
|
New User
Joined: Jan 2015
Posts: 14
Likes: 0
Could that possibly cause the false neutral without throwing any codes?