Chrysler Repair: transmission limp mode/code P0172, throttle position sensor, solenoid pack

Question
1998 Chrysler Cirrus 2.5L V6 automatic transmission.
Q1. Infrequently, the transmission won't shift into 3rd gear.  Turning the car off and then back on fixes the problem.  There is a transmission solenoid code pending.  Any thoughts on how to diagnose and fix this?
Q2. I am getting a rich bank one code (P0172 I think) and the check engine light is on.  I clear it, it stays out for a while, then comes back on.  Any suggestions on how to track down the root cause of this problem?  I do have a scan tool that will read freeze frame and live data, but don't know what normal values should be so I'm having trouble isolating the cause.
Thanks.

Answer
Hi Dec,
The refusal to shift out of 2nd is called 'limp mode' and the trans controller does that when it senses an issue that might cause damage if allowed to operate in all gears. If you have a solenoid code then that means either a problem in the solenoid pack proper or the wiring between the pack and the tcm. The pack can be replaced without removing the trans from the car, so many people try replacing the pack.
Then if there are no other oxygen sensor codes then you might want to verify that the heater of the upstream sensor is continuous.
Then check the alignment of the timing marks of the cam and crank sprockets.
Then using you reader check the 'long term adaptive' value to see if it is outside the value of -18 to -25%. If not, then the cause of the code is no longer present. If it is, then check the wiring of the upsteam oxygen sensor. If that passes, then check in order:
coolant temp sensor, throttle position sensor, MAP sensor, evap emission systet, EGR valve, intake air sensor. and one of which could cause the code.
Roland