ABS light on

The vehicle speed senssor is in/on the transmission. The rear axle ABS
sensor is in the differential. Since the symptoms also include a
speedometer problem, I'd bet on the vehicle speed sensor, not the ABS
sensor. If the VSS goes south, the transmission will show a fault, the
ABS will show a fault, and the speedomter won't work properly. If the
ABS sensor in the rear axle goes bad, only the ABS is affected.

Ed

My apologies. YOu are 100% correct. From the 1999 Service manual:

"Vehicle Speed Sensor (VSS)

"The VSS has been deleted for 1999. On vehicles equipped with 4-wheel
anti-lock brake systems (4WABS), the vehicle speed signal is generated
by the rear anti-lock brake sensor and sent to the 4WABS module. The
4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to
all systems that require a vehicle speed signal input. Vehicles equipped
with rear anti-lock brakes (RABS) generate a vehicle speed signal from
the rear axle speed sensor. The generic electronic module (GEM) receives
this signal (VSS_GEM) for internal use and then distributes it to the
appropriate other users (i.e., the powertrain control module [PCM],
speed control module, and speedometer)."

Sorry for talking out of turn.

Ed

So no apology to me????
Wait and see if I ever help you again

Just to add a year later, get it from the dealer as the parts store vss exits straight out of the top. The orig. exits at a 90*. Parts store will not clear.

Hi, i have a similar problem on my f250, 2000 abs stay on and speedometer go to cero, finaly i find the problem on the ABC module a have to change it for another module (i buy a used one) and everything back to normal,

i hope this was helpfully for you

best regards,

Carlos Valladares from Honduras, Central america

Yep, the vss is what I replaced when the spedometer on my f350
wouldn't go above 0. It was on the rear differential. Look in the
book.

Odds are great it is the speed sensor in the differential.
Cheap part, easy fix - if you don't shear the bolt taking it off.
Could also be in the wiring from the sensor, but I bet it's the sensor

...

The speed sensor is located on the transmission according to the manual I
found at the library. I hope to get under the truck when the weather permits.

Both your manual and you are wrong.
It's on the rear axle.
Period.
Not on the R4100 tranny.
On the axle.
8mm bolt.
Drop the spare so you can get to it.

...

Now that I think about it might be a 10mm...take both under there with you.
Stop by Ford and p/u the sensorit's less than $20.00

...

You likely need a vss (vehicle speed sensor). Ford should have the
part for around $20.