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VSS Issues 


After gassing up the SHO yesterday, I pulled out of the gas station
and the CEL pops on. I also notice there is no speedo movement. The
code was P0500 (Vehicle Speed Sensor) which wasn't surprising
considering the speedo wasn't responding.

I'm trying to figure out what could have triggered the issue--it was
pouring rain and I had to drive through about a foot of water to get
on and off the base (happens every time it rains hard) but that's the
only significant event that has happened lately to the SHO. Never
caused any problems before. I can't see much w/o pulling the wheels,
but there doesn't seem to be any debris on the hubs.

I know one of the front VSSes gives the input for the speedo so I'm
thinking about replacing them to see if it fixes the issue. AutoZoo
has them in stock (Wells brand) for $14.99. Should I just replace
them both? Seems like it would be quick and relatively easy.

Dan Carman
Philadelphia, PA
VSS signal comes from the ABS unit and the wheel speed sensors on the
SHO's...there is an OSS output shaft speed sensor, same as the old VSS, but
it should not be involved with the speedo.

Brent Savage
Yeah, I'm thinking it's one of the front VSSes or the hub ABS ring(s).
The sensors would be the cheap way out but I'm not that lucky. I
already had to replace the driver side CV axle because the ABS ring
was cracked in two places. Maybe the passenger side recently let go?
Looks like the wheels will have to come off tonight.
Dan Carman
What year is your car?

Yes, Vehicle speed ideally comes from the ABS module, one bad sensor shouldn't cause a loss of speedo indications but certainly would power the ABS light int he dash..

Try reseating the ABS module plug (just in front of and below the battery). Also ensure your ABS light tests when you turn the key on, if you have a problem on one wheel speed sensor it will pop the ABS light (as long as it works).

The 96 PCM's may require the "old school" VSS from the tranny for speedo display. But I can say that when I had speedo problems on the 99 the POS Bosch ABS module was the culprit.

Scott K
(I put the Beaker thing in there  U.L.)
It's a '97 (January build.) The ABS light works (verified by turning
the key on w/o starting the car) but does not stay on after startup.
The speedo is still not working at all, but now the CEL has gone away
(checked that one w/ the key and it still works, too.)

Another thing I just noticed is that the SARC is staying full active
(stiff struts, reduced PS assist) so now I'm thinking of a bad ground
or a wiring issue, perhaps brought on by the water. We are starting
to dry out here so we'll see what happens this afternoon.

You would think that the custodians of a federal installation would be
seriously concerned about a flooding issue at one of the
entrances--especially since it's been a problem for several years.
They just added extra storm drain grates last year, but any idiot
could have seen that the bottleneck is underground, so of course that
did nothing to alleviate the problem. This place really irritates me 

Dan Carman
Well, the speedo seems to work from 0 up to about 10 or 12 mph, then
it drops back down. Same with the odometer. Bizarre. Maybe my speed
sensors are full of water or something.

Dan Carman
Nope - your ABS module is BAD.. Same symptoms we had on our 99, boy does the tranny get ticked off when the vehicle speed drops to zero around 20 or so...

Raped by Bosch again you are....(In his best Yoda voice)

Scott K
FWIW Either front wheel rotating will drive the speedo. And I would not be surprised to see if the rear wheels could drive the speedo. But if no speedo then no abs module output......

Paul N
See also:
Speedo Error
Speedometer Failure at Speed 

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