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Originally Posted by mrgoomis
Ok so I'm working on my friends car (98 VW Beetle, 2.0L Auto)
The speedo is fluctuating and becoming inaccurate when the car gets over about 45mph. The speed sensor was replaced once and it fixed the problem for about 2 days then right back to the same. (Someone else replaced the speed sensor) I figured I would give it a shot, replaced the speed sensor again and put the oring in this time. Works! (for about 20 minutes)... 
I hooked up a tester and got capture readings from OBDII connection, captured readings seem to be way off and are about 5mph below what is read on the speedo, but thats another issue i suppose. Speedo said I was going about 40 when I was zipping past cars on the freeway
Since the tester readings are innacurate even right to the computer I presume it is not the cluster, but something causing the sensor to go bad?
I Am STUCK!  Please help with any suggestions! |
My book says:
To ckeck the VSS operation, backprobe the 2 wire terminals on the VSS connector using suitable probes. Connect a voltmeter to the probes and turn the ignition on. Hold the right front tyre steady and rotate the left front tyre by hand whilst watching the voltmeter. The sensor should produce a fluctuating voltage of zero to approx 5 volts.
Other than that it says that the VSS is triggered by a toothed rotor on the output shaft - could this be misalgned or somehow out of kilter and the VSS is not getting the trigger it needs? Good Luck anyway mate.