I had both front hubs wheel speed sensors fail within 6 months. One from NAPA, and one from Advance. As a start, disconnect the driver's side WSS and measure the voltage on the wiring harness with the key on. Then do the same on the passenger side. How does the "good side" compare to the "bad side"?

I don't know how well it will match up, but that is how I found a broken wire on my son's Grand Prix's rear hub's harness. One side had 5 volts, the other side had zero.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

The hub assemblies that I used were National.

The wire was good, the back of the hub was loose.
Replaced with a new hub assembly today - that was it.
The dash "abs off" "Trac Off" lights are no longer lit.
The traction control switch by the shifter is now lit up
like it should be.

Took it for a test drive - the "service stability system"
appeared on the DIC eventually. It no longer comes
up at start up, but once the car hits 15 MPH or so
it comes on.

Thanks for the help.

Great. Happy to hear that that part of it is fixed. When it was scanned, was any other problem found. There are other causes, but the most common for the stability system is the steering position sensor.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

The other codes were a bunch of transmission codes - it has the "hard shift" issue.
Very rarely the transmission will hard shift. Once the car is turned off it stops
and will not come back for a long time. I have thought about installing the "shift
kit" to fix this issue. I replaced the front motor mount last summer thinking it may
have been the cause but it was not. I did a manual trans. flush+seafoam which helped to cut
down on the issue. The car also has the intermediate shaft clunking going on
with the steering.

I think that it is code P1811. My son had that problem on his '99 Grand Prix. Installed the shift kit coming up on 3 years ago, and the problem has not returned.

Do you know if work was previously done on the steering shaft? If the steering wheel was turned too far during that, it could have damaged the coil on the position sensor. Follow the procedure in techinfo on lubing the shaft. Since I wrote that, the clunking has not returned on either car that I did it on.

Unfortunately, you'll have to have the car scanned again to find out the reason for the service stability system. Have it scanned while it is still displayed on the DIC as sometimes the code just disappears when the car is shut off.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

Drove the car to Minneapolis last weekend and the handling was terrible.
Wife's car - I don't drive it regularly...
Anyway the back end of the car was all over the place. I looked under
the car and noticed the Driver's side rear shock was blown - lots of fluid leaking.
Took the shocks out - they were shot! Bought a pair of Monroe air shocks
for $74.99. That was the handling problem - it's like a different car.
Have not seen the "Service Stability" message come on since - don't know
if the two are related or not. Could the level ride system be part of the
stability system? We will see if it comes back on.

On the plus side - I was glad to find out it had rear shocks and not struts!

Thanks for the help!

The shocks are about the easiest ones that I have replaced on any vehicle.

As for the stability system, I believe that bad rear shocks can cause problems...more because of experience than anything that I can point to in the operation of the system. If the right rear would hit a sharp bump, it would set off that warning, until I replaced the shocks. Then, I no longer had that warning come up.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.