"Help" I Have A Speedo Fault.

[danmar333]

Please can someone help, I have a "98" Explorer sport which has encountered a speedo fault, It started when the speedo needle bounced about a bit, then it progressed to starting off well then half way through a journey it just failed.
I did some research on Alldata & it said that the VSS Vehicle speed sensor was operated by the rear ABS sensor, so I crawled under the car & found no ABS Sensors on the rear, so whilst under I cleaned up the fronts, Also whilst under I removed & cleaned a sensor located at the rear end of the Gearbox. the next time I drove it the speedo worked all day, then just when I thought that the fault was cured, Yes it failed again.

Please any suggestions.
Many thanks Dan

 

[BrooklynBay]

Welcome to this forum! I've moved your thread to the transmission section. It's possible that the VSS is faulty.

 

[dogfriend]

so I crawled under the car & found no ABS Sensors on the rear,

There is a single ABS sensor for the rear axle, it reads a tone ring (toothed disc) that is mounted next to the ring gear inside the differential. You should find the ABS/VSS sensor on the top center of the rear axle.

 

[dogfriend]

Here is the drawing from the 99 Manual:

 

[gijoecam]

The Vehicle Speed signal is generated by the ABS Control module. The ABSCM takes the inputs from the front wheel speed sensors and the single rear axle speed sensor, processes the signal, then outputs it to the PCM, GEM, Stereo, Instrument Cluster, and Cruise Control Servo among others.

Soooo... When the gauge goes flat-line, does the cruise still work? Does the odometer continue to roll? Does it shift fine? If everything else keeps working, IMHO, it points to a gauge issue. if all that stuff dies, I would suspect a VSS signal issue from the ABSCM... whetehr because it's gettign bad data, or because it's failing itself, I have no clue....

-Joe

 

[danmar333]

speedo fault

Thanks Guys for the info so far, I will keep pluging away at it.

Thanks.