About a year ago my speedometer started jumping around after a day of track time at Road America. The next morning it was fine. Checked codes and got nothing. On the way home it dropped dead and I almost selected reverse on the up-shift from 4th to 5th. The likely culprit seemed to be the the VSS (Vehicle Speed Sensor) which is a proximity sensor located on the top RH side of the differential.

This got worse as the weather cooled off in fall, but it never threw a code. This summer it resolved it self to dead speedometer for the first 500 feet in the morning and then fine for the rest of the day. If the speedometer is bouncing around skip 5th gear and go from 4th to 6th would be my recommendation.

Finally it dropped dead and check engine light came on. Code was P0500 so I ordered a new VSS for about $50 from a CF vendor.

I backed the car up on ramps to replace the sensor. There is not a lot of room between the top of the differential and the body to work in. I used a mirror on a stick and could see that there is just one screw holding the sensor in place. I used a 1/4" drive ratchet with a 10 mm socket to remove the hold down screw. It's really long and you can't turn the ratchet more than 90 degrees at a time, so it took a while to remove the screw. The sensor then just pulls out, and you plug in the new one and reinstall the bolt. I used the mirror to line up the sensor bracket with the tapped hole. You can't see it and get your hand up there at the same time, so it is a bit of a trial and error process.

The bolt had some sort of green goop on it (Loctite?) which was not hard to break loose, but after removing the screw it closed up the entrance to the tapped hole. I could not get the screw thread started so after 5 minutes of trying, I pulled the sensor and tried to remove the goop. It's very difficult to get any tool up there and because I was working by feel, I could not remove a significant amount of goop. I finally was able to get the screw started in the hole with the sensor removed. I did about 5 revolutions on the screw before removing it to make sure I could get it re-started with the sensor in place. The sensor has a slot, so its a little difficult to figure out or feel where the hole is.

After installing the electrical plug and starting the engine, the CEL was sill lit and the P0500 code was still showing current. I cleared the code and drove around and now everything is fine.

Things that VSS failure effects:
Reverse lockout solenoid
Speedometer
Heads up display
Cruise Control
Automatic door locking at 10 MPH (or whatever the speed is)

I was surprised that the VSS could be intermittent. I figured it was a bad connection in wiring.

Hope this helps someone.

 

Excellent write up and thanks for taking the time to detail the replacement.

Bill

 

Thank you!!!

I have used your write-ups to fix my car on several occasions.

 

Here is what sensor looks like:



It not that difficult to reach. I worked mostly by feel.

 

Thanks for that information.

Do you think that the difficulty in getting the bolt started was more the green goop , or perhaps that the hole for the bolt in the new sensor did not line up quite right?

 

No, it was all the green stuff. The steel bracket for the sensor has a slot to account for tolerances.

 

I imagine green goop to be dielectric grease, but who knows. Great writeup, thank you.