Broken tooth in speedometer head. Replace speedometer head
It is non-servicable, so repair requires replacement of the speedometer/odometer assembly.
If the speedometer and abs light are not working then you have a speed sensor problem. If the speedometer or odometer are not working then you will need to take it to the dealership and have them send it off for repair.
Need to figure out what's wrong with them, first.
If your odometer/speedometer stopped working, then you must replace the "vehicle speed sensor" located on top of the differential if your have a manual transmission.
Stepper motor for speedometer has a broken gear in it, causing unpredictable operation. If the odometer is still working, then the speed sensor is OK. Instrument cluster needs repair.
There are two possible actions: 1) Replace the speedometer head assembly, because that is where your problem is. 2) Ignore the broken odometer and forget about it. The speedometer and odometer are one assembly. The same input that drives the speedo also drives the odometer, so you have a problem in the head itself.
Need to know what is wrong with it. If both the speedometer and the odometer don't work, I would suspect the VSS (Vehicle Speed Sensor) located in the back end of the transmission is bad. If only the speedometer doesn't work, I would suspect the instument cluster has to be replace with a reconditioned one from your local Chevrolet dealer. Contact a dealer for a price.
Disconnecting the speed sensor stops the speedo and odometer. The odometer has to be changed by a certified speedo repair shop.
check the vss located on the tailshaft of the transmission for the speedometer issue the odometer is figured out based on the speedometer also so it will quit as well. this sounds like either the sensor is bad or a short in the wire from it The cord for the speedometer came undone from the transmission or the gauge cluster is bad
The -E-ngine -C-ontrol -M-odule, or ECM recorded the vehicle mileage along with the odometer. The EMC mileage can be read by a scan tool at most dealerships or repair shops with the proper equipment. It is possible for the two mileages to differ slightly, but a large variance may indicate a faulty odometer, or possibly odometer tampering.
The best way is to buy a book on your model and see if you can do it. Then! Ask again on this sight for help when you feel confident that you know what your doing to repair the speedometer.
According to my Haynes repair manual, 1996 and later models do not use a conventional speedometer cable. They use an electronic speedometer and a vehicle speed sensor (VSS)