Vehicle Speed Sensor

[denislmorin]

I have a 1994 E-350 Econoline Motorhome. When I drive on the Highway the speedometer goes haywire, my ABS light is always on and sometimes my cruise gets disengaged. After reading up on the problem the likely culprit is the Vehicle Speed Sensor. Any idea where this is situated and whether it can be changed by myself? Thanks

[CaptainCal]

My 95 does the same thing. I had to replace the vss several times. I did find that metal shavings in the rear differential lube can cause the vss to give false readings at speed. They are magnetic and will pick up metal to distort readings.
My abs light is also on all the time, can't find out why with all test done. I just live with it.
The cruise control would some times work, some times not, and have a mind of it's own. Replacing the pressure switch on the brake master cylinder sloved the problem.
Ford's of his age are known for having speedometer problems. Sorry I can't be of more help. Good luck.

[denislmorin]

The Instrument Cluster has been replaced, the VSS had been replaced, the wires have been traced and still have the same issue....:( What next?

[denislmorin]

Well the cluster on the speedo is good. I am getting though 1700 ohms when I test the new VSS. Does anyone know what it should read? The new VSS is not a Ford original though. Could that be the issue? Thanks

[bfast54]

If you're going to continue to throw parts at it instead of getting expensive mechanic involved ( which at this point you may be done throwing parts ,because you replaced the first culprit)..go to Rock Auto -----rock auto.com .


I ordered a vehicle speed sensor for my rear end of my truck ----is pretty pricey at $9.41:W

Check your wiring harness carefully...could be a snag somewhere.

[fortytwo]

My 2000 Class A had 3 different speed sensors (all are identical so you can swap them back and forth) on the rear axle. Each apparently fed different info to the engine computer. Yours is pre-V10 so not sure how your engine is programmed, but obviously some sensor is feeding incorrect info to the speedo.

Mine turned out to be a bad ground in the ECU wiring harness. My wiring harness had 7 different ground wires. Just takes one to corrode and change value (voltage) to the ECU to create all kinds of wild results. Computers controlling your engine are great --- when they work. When they act up trouble shooting can be a real joy... Diagnosis can approach the cost of a new engine.

[denislmorin]

Acts the same after I changed the VSS on the differential (When I drive on the Highway the speedometer goes haywire, my ABS light is always on and sometimes my cruise gets disengaged.) I have now disconnected the battery. I am wondering is the speed sensor on the transmission is defective. I am still trying to locate the speed sensor on the transmission.

[j-d]

Does it ACT any differently, or do you mean only that the LIGHT is still on? Your 1993-or-94 chassis is OBD-1. Of course that means it's pre-OBD-2 which means you can't use the common scanner or OBD interface to your Droid Phone or Tablet.
Somewhere, there's instructions how to scan for ABS codes in pre-OBD-2 Fords. I don't think it was at the same trapezoidal-looking connector under the hood (probably near the driver side hinge near brake booster) as the OBD-1 code terminal. And I don't remember if it had "Reset Codes" included.
A quick gOOgle search said "disconnect negative battery terminal 30 minutes." Worth a try.

[denislmorin]

By the way does anyone know where I can find the other speed sensor on the transmission?

[denislmorin]

Well I replaced the VSS on top of the rear differential and still have the same problems. I noticed there is another part next to the VSS on the differential. Not sure what that one does? Any suggestions besides getting a mechanic involved? Thanks

[j-d]

^^^ Agreed, and as I mentioned above, I think OP will find other systems acting strangely if the VSS has in fact failed. Could be something else, but VSS failure isn't uncommon and it's cheap enough to throw at the problem to see if it goes away. ...And small enough to carry as a spare...

[Vulcan_Rider]

denislmorin wrote:
I just got it safetied and I was told by the mechanic not to worry about the ABS light being on.

And I think you need a new mechanic.

While that light is on, the ABS function will be disabled.

It doesn't take much hard braking to get a high center of gravity vehicle a little sideways so that it flops over on it's side.

[denislmorin]

Thanks You J-D and Tommykelly and others. I will try over the next few days and will let you know the outcome.

[tommykelly]

same thing on a '99 f350 dually...unplug the sensor on the rear axle .make sure connection is clean and put just a little electrical grease and put plug in making sure it is properly connected....try the cheap way first...I bought a new sensor and did not need it.

I use spray electrical cleaner

[j-d]

The VSS went out in our 1992 Ford Van. Cruise, Speedo/ODO, and Overdrive would not work.
Part is available at common parts outlets. Ask for your CHASSIS model year, which may be earlier than that of your coach. Look for Ford's VIN label in the driver door frame. Date of Manufacture will tell, so will a Position 10 of VIN. 1993 = P, 1994 = R
CLEAN the area on top front of the differential housing. Remove one retaining screw with 10mm socket. Check wiring connector for release tab. Release and unplug. Transfer O-Ring to new VSS if not provided with part. Lube O-Ring, reinstall, tighten screw, plug wiring back.