First and fore most I know this subject has been covered on a few forums, but a full answer has never really been given as there can be different solutions per each situation hence the thread title. Subford has been helping out on a different thread and I thought it was best to not bury it in a thread not titled for the fix.

1992 Ford F250 XLT E40D 7.5L 4X4 is the truck.

Code 11 Pass Code KOEO

Pretrip
The RAB Light is on steady.

On Trip
(RAB Light on whole trip)
The situation is the truck will run normally for a few blocks down the street in drive, but at some point the truck will not leave 1st gear (Limp mode) the odometer needle won't display speed anymore either.

What I've Done So Far
1. Done the needle sweep test by holding down the trip button on the odometer. The needle does a full sweep and goes back to 0.

2. I ran continuity from the psom connector pins to the pins on the vss connector. 001 ohms was shown for resistance on both wires which is to be expected seeing as I was using a 10 FT extension on my multi meter.

3. I visually inspected the wire harness for any damages.

4. I checked ground connection G200 which is the common ground connection for several things to do with the psom, vss, rab. All wires accounted for.

5. I checked all the fuses with a multi meter and even pulled them for the hell of it and looked at them. They fit back in the fuse box nice and snug.

6. I ran ohms on the speed sensor 1550 ohms.

7. I replaced the speed sensor with a ford speed sensor for giggles. Ford sensor runs at around 1800 ohms.

8. The PSOM has 0 corrosion or burn marks.

Currently I have a PSOM coming in the mail that is supposed to be in working order so I will try it when it does.

I haven't opened up the differential yet because the abs light is on full steady and I am pretty sure it has nothing to do with the vss or tone ring in the differential at this point.

Is there anything that I haven't thought of yet because this is really starting to get to me that I have a truck that I have not driven for more then 10 mins at this point.

 

Suggestions?

 

1. Unplug the RABS Module and see what happens.

2. Check the input from the VSS at the RABS test plug under the hood by the EEC Self-Test plug with the truck on jack stands (for 4X4 all four wheels off the ground or drive while someone else is watching the voltage).
Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts AC as vehicle speed increases from 0 to 48 km/h (0 to 30 mph)?

The KOEO test has nothing to do with the VSS & speedometer head. But there will be a code in CM for the VSS after the KOEO test is done.

 

Before unplugging the RABS controller, pull the codes from it.

RABS Information

 

"There are certain faults (those associated with the fluid level switch or loss of power to the module) that will cause the system to be deactivated and the REAR ABS light to be illuminated, but will not provide a diagnostic flashout code."

So I tried to pull codes off the rabs test connector. The light is steady and I was given no codes. The brake fluid level is good... Now what?

 

If the red brake light is on you cannot pull the codes.

A 1992 model year truck uses RABS-I so the controller will keep the codes until you shut off the truck. You have to pull the codes when you have an active ABS light and before switching the truck off.

 

Tested with e brake on and off. Tested with truck on and off the light is always on after 3 secs of key turned. Tried with different ground point. Back probed connector and from probed. Also probed at connector.

 

Then it looks like you have a seriously bad RABS controller. If it will not reveal what the issue is to trigger the yellow ABS light, then it's time to disconnect it to see if it is also causing your speedometer problem.

 

Alternate test to test 2 in post #3 above.

Key OFF.
Remove the harness connector from the anti-lock electronic control module.
Raise the vehicle so that all the wheels (1007) are clear of the ground. If the vehicle is a 4x4, verify the transfer case is in the 4x2 mode.

Connect a Hand-Held Automotive Meter between harness connector Pin 10 (Circuit 523-R/PK) and Pin 3 (Circuit 519 -- LG/BK).
Set the meter to the frequency counter (Hz) setting.
Gradually spin up the rear wheels.
Does the frequency increase as the rear wheel speed increases?

Attachment 277289

Attachment 277905



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Reread the rab code list. It says if no codes flash check master cylinder connector. I know what it is and will check after work before I do the 0 to 30 test light subford suggested. Is there anything I should know about that connector to check 4 to know it's working?

 

Alright good thing I reread the error rab list. Even though my master cylinder connector is fully clicked into place apparently the wiggle room allowed the abs light to be on.

I will take the truck out for a test and pray it doesn't go into limp mode and get stuck in first.

I ran koeo and koer both which gave me a display of pass code 11. So hopefully the problem is fixed however I still don't see why abs light being on would kill the speedometer 5 mins light driving around and force into limp mode. Will update after test drive.

 

Tried a test drive every bump I hit made the rab light turn on then off, speedo went nuts every time. I duct tape the connector in and after a few good bumps same thing. Back to odometer screen going blank and speedo not working. I can't tell if it shifts to 3rd or 4th. No rpm gauge in the cluster and I can't feel it shift. I don't think it's going past 2nd, but can't confirm. The truck died all together at a stop. I assume due to overheat redline happening. Does this give clarity to what the problem is? I want to blame the connector at the master cylinder, but that doesn't explain lack of shifts or speedo freaking out. Even check my cluster witg a good shake to recreate but nothing.

 

I have had D1 on the PSOM borad come loose and cause that. It is surface mounted.



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Did that give you shifting issues as well? I did take a good luck at the board when I pulled it for loose diodes and stuff as well as looked at soder joints. Will pulling the rab connector bypass the loose plug on tge master cylinder? If it gets pulled slightly out rab light comes on. I duct taped it down trying to test if it was the issue however still happened prob from tape n heat not going well.

 

Well no but that one came from a 1997 F53 and they do not use the PSOM to send the speed information the PCM or speed control.
The speed sensor (VSS) sends speed information right to the PCM for the E4OD on the F53 and the VSS is located right behind the transmission.

Yes it would.