Where is the speedometer censor located - 1991 Plymouth Sundance

you may have a bad speedometer gage.

clean the abs censor and check wiring at brake end might just be **** on the censor

If your Neon is running, go to one of the chain auto parts stores and ask for a free scan of your computer's error register; it may have one or more error codes stored.
If you plan on any DIY work, I suggest you invest $25 in a Haynes manual for the car, You can get these at most all parts stores or on line:
Haynes Neon manual

Sounds like bad speed sensor. Will probably loose speedometer also. Should get scanned as soon as possible to locate problem.

there is 4 wheel speed sensors on each hub.
your speedometer is controlled by your abs module.

It is either stuck and will need to be moved by hand or you need a new speedometer cable or censor.

Go to Autozone or Oreillys and get a free scan. Sometimes the alternator can cause the speedometer to give false readings. The parts guys can show you where the parts go. The sensor should not be too hard to replace.

What type of car is it? Most front wheel drives have a 3 wire plug on the top of the transmission.

see my comments, not 100% sure that it was the out put speed censor or not, but after reconnecting the wires to a new censor and reconnecting the battery and clearing codes it worked. connection was not clipped may have been loose

i have a 1997 buick century speedometer was working until i changed the cluster and now it doesnt work does it need to be reset, please help me or a new speed sensor