Vehicle speed sensor malfunctioning--2000 Ford Taurus

Maintenance/Repairs
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1

I need your help in figuring out what is going on with my dad’s car. This car is a 2000 Ford Taurus with about 160,000 miles. In the morning, when he starts the car and drives away, sometimes the speedometer will not work and the automatic transmission will not shift out of first gear. After a few miles, the transmission will suddenly upshift and the speedometer will jump from 0 to the current speed. The door locks will also lock at the same time (they normally lock upon reaching a set speed). However, the car can be “forced” to shift, start the speedometer, and lock the doors by accelerating to 5000 RPM. The problem appears to have something to do with the vehicle speed sensor, but I don’t know what exactly is wrong with that system. The car also knows that something is up as the Check Engine light is on.

  1. What might be wrong with the VSS that causes this problem?
  2. Why can it be forced to shift at 5000 RPM?
  3. How much will this cost to fix?

Thanks for your help!!

2

First, get codes. Even if the CEL isn’t lit.

3

The VSS on the Taurus is a variable reluctance Hall Effect sensor. It is driven off the final drive of the transmission. As with all solid state devices, they can become intermittant. Heat and vibration can make them work again.

If you had a way to patch into the circuitry you might be able to see if the sensor is working i.e. producing a variable frequency voltage. The sensor has to have power and a front wheel has to be turning. If you see the voltage at the sensor, check again at the PCM

The quickest way is to just replace the VSS. It is accessible from outside the transmission. The Alldata part cost is $62.78 and labor is 2.7 hours?. I have no estimate on the diagnostic time.

Hope this helps.

4

This is a common problem on all years of the Taurus. Its an easy and cheap fix. The part is around $44 at the local parts store, and you can find a video on you tube on how to replace it. This is something that can be done on your own without paying a ton to a mechanic! $43.99 Each. Part Number: SN7195. This Is at Oreilly auto parts. http://m.youtube.com/watch?v=y0823ZDqxiU&desktop_uri=%2Fwatch%3Fv%3Dy0823ZDqxiU&gl=US…this is once of the videos.

5

Thank you for your help, guys! I’ll probably be asking more questions eventually (but not now).