01 Sunfire, 2.4 L, High RPM/Gear Change Problem

[TheFlyingPenguin]

Hello,

I posted this question about ten hours ago, but I'm not sure if it went through properly. If it ends up double posting, please delete one of the threads.

My car is a 2001 Pontiac Sunfire, Automatic, 2.4 L engine.

My issue is that the car doesn't seem to be changing gears. I believe it changes gears once when I first start driving at low speeds, but doesn't kick into the next gears after that and the RPMs go up very high when driving.

The check engine light is on and I scanned it with a scanner I have here at home and got the following code: P1810. Which indicated a malfunction of the ATF Pressure Manual Valve Position Switch.

I brought the car into a transmission shop and they said they believe it's a faulty wire located somewhere under the hood. They haven't searched for it yet, though, and I have an appointment Wednesday for them to look for it.

However, in the meantime, I was wondering if there were any suggestions on things I could do to troubleshoot this issue? Also, could anyone point me in the direction of the wire that the mechanic would be looking for to check for faults, so I could possibly look for it myself?

Thank you for any assistance.