There are several speed sensors, perhaps you are referring to the "vehicle speed sensor"?
If so I can only assume your speedometer quit?
If the above are true, replacing the sensor will probably not fix your problem.
Usually on Catera when the speedo drops to zero you'll see a couple lights come on as well.
The vehicle speed comes from the right rear wheel speed sensor via the EBCM to the TCM.
If the ABS light comes on also, and you see transmission codes and ECM codes... you probably need an EBCM.
There are several posts on this concern on the forum.
The EBCM is the Electronic Brake Control Module.
It is located just in front of your brake master cylinder and below.
It is attached to the ABS unit.
A factory repair part can cost about $1,300 plus installation.
I usually charge about 3 hours.
I have heard of places that will refurbish yours or sell you a rebuilt one in exchange for your old core.
I saw that mentioned on here somewhere.
You might ask around and see what kind of luck people have been having with them.
It sounds like that is what is happening to your car.
ZenButcher! AKA Peter B.
Yes - I contest - it's more than likely the EBTCM Electronic Brake Traction Control Module...
I have a 1998 catera and had just about the same issue(s): the speedo & odo failed to work and the ABS & TC & ENGINE CHECK lights were ON; but the car drove as normal. But get it fixed ASAP - dont drive it "as is" - you dont want to welcome other problems RIGHT!
A local WI dealership wanted $1500 for a new EBTCM + labor = say $2000 total! I told them to lay-off the crack pipe... I had mine pulled, fixed and installed for under $500! It's a bear to pull so have a [quality/qualified] mechanic do it. I even paid for over-night delivery and personally sent my EBTCM to:
*SERIOULSY! HAVE YOUR ORIGINAL REBUILT - DO NOT DO AN EXCHANGE OK!
Make sure you write the serial# and any associated numbers on the EBTCM before shipping so as to get the original back. ModuleMaster will replace a switch inside the EBTCM and you will pay for the return shipping as well.
Note: Have it shipped to the shop that pulled the unit and they'll install it straight-away. I paid for 2 hours of labor $65 per hour.
Excellent help guys! I took to my shop and went the rebuilt route. Even they b!tched about the design of it. But a total bill of $310 - I'm happy. Speedo works, no dash lights, I'm in Catera heaven. One things for sure, I was lucky I didn't get a speeding ticket while driving with no speedo.