Chevrolet Repair: 97 Chevy Cavalier , auto trans not going into overdrive, brake light switch, chevy cavalier

Question
Hi , my wives 97 Cavalier won't shift into over drive ,,even when i try to shift it manually , my friend is a mechanic , he works out of his garage at his house .  I took the car to a transmission place, the owner  knows my friend , so he took the car for a ride for us and said it's not the tranny ,, it's a sensor causing it not to go into overdrive.  now we put the car on a scanner but , no codes , the check engine light isn't on at all ,,, but the abs , ets traction light come on sometimes ,, they have been coming on and off for a while , but the car still shifted into over drive  , it just recently stopped doing it.    his scanner doesn't do abs ..  could this be the problem . the owner of the tranny place the temp sensor could cause it also ,  he checked it with the scanner it read 175 degs Fahrenheit. he said to check the brake light switch ,, we unplugged it and tried it , still didn't work ,, we tested the switch there is power going to it and completes the loop .. is there any where else to check ,, the tranny shop will diagnose it , but for another tranny shop has a tranny diagnostic machine and is willing to diagnose for 350.00 .  we're trying to avoid that root.. my friends buddy who owns a tranny shop , doesn't have a diagnostic mach ,, he's ready to retire and doesn't want to buy one ,, he said the cavaliers tranny is controlled by electronics.  my freind the mechanic is trying to do me a favor to save us some money and bring it in to a tranny shop. can you please point us in the right direction .  Thanks in advance ,  Randy

Answer
Hey,

 You are going to need a scan tool to see what the PCM is trying to do with shift timing.  Guessing on components at this point is going to be fruitless.  With a good scan tool you will be able to see road speed and solenoid status for each gear and what the computer is trying to do.

wayne