How do you reset the diagnostics on a 1999 Saturn coupe?
The codes have to be removed with a scanner. Go to Auto Zone and they will do it for free.
OBD2 stands for "On Board Diagnostics Revision2" It refers to the way all auto manufacturers are supposed to implement the on board diagnostics. To read the diagnostic codes, plug an OBD2 scanner into the port and allow it to perform it's magic. For your Saturn, the scanner port should be located below the dashboard, next to the steering column.
Where is the speed sensor for a 1999 Saturn S-Series 3 Dr SC2 Coupe The parts is online for 21 bucks and you want to change it out yourself?
You can't. Best advice is to take it to a facility equipped to do diagnostics to find out why it is on and if it is on by mistake they will reset it. If you don't get the diagnostics it could cost you a lot of money. It can be turned off by disconnecting the negative battery cable for a few mins. If its a hard code then it will come back on, mine came…