Erratic speedometer

[Guest xerxes]

Have an erratic speedometer. Have removed the connection to the VSS and sprayed WD40 on it and VSS. Still bounces around rather than reading properly.

Do VSSs often fail?

Is there a code or other software test to help troubleshoot?

Thanks in advance!

[padgett]

ED-12 will display what the ECM "thinks" is happening. Is the odometer reading correctly ? If not I would check for a wiring issue first, if not at sensor then at bulkhead connector or BCM. FSM (8A-82) says to check voltage at VSS with front end jacked up & secured properly and wheel turning (in air).

[Guest xerxes]

ED12 reads "0" - I'll check connectors and reply later...

Thanks!

[Guest Drake]

When I purchased my 89 three years ago, the speedometer would always read 1 to 2 MPH when stopped at a red light. If I inched up, and hit the brakes, it would go to 0 MPH. Odometer registered fine, and seemed to display ok while moving. Last month I replaced the VSS and it is working fine now. VSS is still available through Buick dealer.

[ncgirl05]

ED-12 will display what the ECM "thinks" is happening. Is the odometer reading correctly ? If not I would check for a wiring issue first, if not at sensor then at bulkhead connector or BCM. FSM (8A-82) says to check voltage at VSS with front end jacked up & secured properly and wheel turning (in air).

I am having a similar problem with my '89 - speedometer "seems" to be reading correctly until I go over 40-50 miles per hour, then it starts reading too high - I know for certain that traffic that usually moves at 65 mph did not decide to suddenly go 82 mph when I drive my Reatta. I have a dumb question - quote above says to check voltage at VSS - what is VSS?

Anyone else have the problem? It started after we changed out my alternator. Related? :confused: Don't know.

[padgett]

Vehicle Speed Sensor on the transmission.