Chrysler Repair: 2002 Chrysler 300M tranny code 1776, solenoid pack, solenoid switch

Question
after driving about 20 mi. the check engine light came on and a minute or so later the tranny downshifted into 2nd and stayed there when in D.  In Manual shift selection, all tranny position lights (P R N D 1 2 3 4) on the dash were bright,rather than a single gear postion 1,2,3, or 4.
The car was then parked for 9 hrs.  I then drove it a short distance to Autozone to get the error code (1776) but did not reset it. Tranny worked normal for about 5 miles then at about 40 mph felt a lurch as the tranny downshifted to 2nd again and remained there until I arrived home some 20 miles later. After another 3 hour wait, started the car to move it in the driveway. I was able to select manual positions 1,2,and 3 as normal so I presume the tranny was "back to normal" but I did not drive any distance.
Any suggestions how to check the computer, solenoid, wiring?  Where each component is?  

Answer
Hi John,
The low-reverse solenoid switch is stuck in the latched position. Generally it will be corrected by intalling a replacement solenoid pack, though you could try removing the pack and correcting the issue with the solenoid valve itself. The pack is externally positioned and can be replaced by the owner but it does require dropping the oil pan and removing the valve body first in order to then change it out, so in that respect it is not truly 'external'. But at least the trans doesn't have to be removed. If you don't have experience in that pan drop/valve body removal process you may want to let a shop do it. I can probably copy the manual pages and email them to you, from an '04 shop manual.
Roland