Pontiac Repair: 1999 Grand am shifting problems, auto parts store, engine computer

Question
I have a 99 grand am.  Sometimes it refuses to shift into second gear until you shut the car off and restart it.  I have replaced all the shift sensors to no avail.  Luckily this is no longer a daily driver but I cannot sell the car like this morally.  I had an auto parts store hook the obd reader up and it was saying shift solenoid/performance something or other.  This has the 2.4l motor and I believe 4t40(?) Transmission.  Thank you.

Answer
Hi Ian:

If this car will not shift into second gear it more then lilley has a shift solenoid issue or possably a valve in the valve body is sticking for 2'nd gear. You could also have an issue with the wiring going from the engine computer to the transmission or inside the transmission.. That transmission was noted for connection issues at the transmission where the wire harness plugs into the transmission. The terminals would become loose and cause this same type of issue. Once the code sets the computer will inpeed the transmission upshift in gears and that is whey cyclling the key makes it work again untill the fault occures gain. So My guess is it's an electrical issue more then a mechanical issue but the issue is trying to find the source of the problem..... Good luck :)