Vehicle speed sensor

[nameskreen]

Does anyone know the test procedure for a vehicle speed sensor on a 97 Mountaineer 5.0. Mine is the VSS that's in the transfer case. My speedometer and odometer stopped working suddenly and then I got a VSS Code P0500. I changed the sensor but it didn't fix anything. I hooked the old sensor to a drill with my meter attached and when I spin the drill, the voltage increases. I plugged it into the vehicle and spun it with a drill with key on - engine off and the speedometer does not move. I looked in the sensor hole with a boroscope and the drive gear looked ok (at least from what I could tell) I'm not really sure what the problem is. Thanks

 

[nameskreen]

I also had 4.7 volts at the VSS connector with it unplugged from the sensor. key on/engine off

 

[J_C]

When you spin it, seems like you should get a low voltage AC signal out of it, unless there is a diode built in, then even lower voltage DC.

Engine off, you have no *computer* to interpret that and turn it into a speedo signal. I suspect the sensor is fine and some other problem exists , but I don't know what. I'd search that or look for youtube videos if someone doesn't come along with experience for the same issue.

Code P0500 - Google Search

 

[nameskreen]

Thanks. I thought about it after the fact, that maybe the vehicle needed to be running. But by then it was pouring rain. I'll retest it after work.

 

[Pete Deering]

This is what I found

 

[Pete Deering]

When I looked up parts, there around $20+-. But there two sensor listed. Input and output.
The output goes too the cluster. They are a signal generator(AC). Did you scan for codes? From my experience , when the VSS fails the cluster goes crazy.

 

[410Fortune]

4.7v is correct this sensor runs on 5v

Try the drill test with the truck in the on position or running and see if your speedometer
Moves

The drive gear gets worn down the middle and then will No longer spin the driven gear or it will be intermittent.
Scope is good but you can also feel the grooves on the drive wheel with your finger

The sensor itself must have both wires going to the PCM
You can test the circuits with a continuity test between sensor and the appropriate pins at the pcm

The two things that wear out or fail on a 96/97 speed sensor would be the drive gear gets worn out, sometimes due to a bad sensor causing excess drag, or the little gear in the odometer itself will strip
Leaving you with no odo
Otherwise the system is pretty tough

 

[Pete Deering]

When I looked up parts, there around $20+-. But there two sensor listed. Input and output.
The output goes too the cluster. They are a signal generator(AC). Did you scan for codes? From my experience , when the VSS fails the cluster goes crazy.

 

[410Fortune]

Interesting info about the epc solenoid issue resulting in false p0500 hmmmmm I have a p0500 on my 5 speed converted 302 sport trac I am unable to get rid of
Maybe need some More pcm Tuning

 

[Pete Deering]

Test procedure of VSS

 

[nameskreen]

I checked again after work. I started the vehicle and spun the sensor with a drill while plugged in to the VSS connector and the speedometer did not move. I hooked my meter to the sensor (unplugged from the connector) and spun it with the drill and I did get pulsing ac voltage. I haven't done an all module scan, only a check engine scan, which was the P0500 code. We do have a Snap On scanner at work that I can borrow. I will dig a little deeper this weekend and post any findings. Thanks again.

 

[nameskreen]

I scanned it again today. The P0500 VSS Code is still there. I drove with the Snap On scanner hooked up and it read 0 mph while moving. I double checked : power at the connector, the odometer drive gear with a camera, etc everything looks good. I pulled the cluster, I didn't see anything obvious but I didn't take it completely apart either. So I'm not sure if a bad cluster could be my problem or not

 

[410Fortune]

The pcm is not seeing the speed sensor signal

 

[nameskreen]

I went out again and checked for ground at the VSS connector and I was missing ground. After more Google searches I found out the pink ground wire terminates are the driver inner fender. A mouse chewed the wire. I spliced in a new wire and it's fixed!. Thanks everyone