I bought a speed sensor and i need to know how am i supposed to change it in a 1997 chevy cavalier. Do i take the transmittion apart or what? and where is it located the speed sensor

Yes, CHANGE THE SPEED SENSOR.
See the diagram for location.

check your throttle sensor

by the oil filter 8mm bolt holds it in.

Catayltic conveter plugged . Have someone do a back pressure test. Don't know where or how you came up with code P1702 , it's not a valid chevy code .

Best suggestion is go to your local GM parts department and as them for a print up.
If they are not sure about giving you one tell him you need some parts just have to be able to get it
apart and figure out which parts it is exactly you need.
A good partsman will even help you out.
Cheers

the vehicle speed sensor is going bad.

Possibly bad tpos sensor

Bad idle air control valve

Bad maf sensor

Check the computer codes first before spending any more money on it

Also do a compression check

And check your valve timing and ignition timing just in case.

The speed sensor for your 1991 Chevy Cavalier Z24 is located on the transmission just inboard of where the passenger side drive axle enters the trans-axle.

If the coolant level is o/k check level indicator sensor which should be on the rad. It is a one wire sensor. Hope this helps. Moe

the problem is the crank shaft position sensor ! I just replaced it on my wifes and it runs like new....