How do I troubleshot without going through all 4 possible causes

Question

01 cavalier, vehicle speed sensor circuit low input. All 3 symptoms popped. Question is, what would most likely be the main problem, just to avoid going through the 4 possible causes. I'm not a car guy so any advice would help.

Answer 1

What are the code that are set. this would help to determine if the cause is a internal mechanical issue with the transmission or just a faulty sensor.