Hello, I'm Richard! I'm a Chrysler dealer tech with 22+ years experience & I'm going to try my best to help, so let's get started!
There are many things that can cause the transmission
to go into limp-in mode. When the TCM sees a problem that could harm the transmission, it will go into limp-in mode.
When the TCM is in limp-in, it will turn off the relay that supplies power to the transmission solenoid pack.
The TCM will have a fault code stored and we need to get the TCM fault codes read before I can say what's causing this. Lets try the key cycle procedure to see what PCM codes are stored first.
Sit in the vehicle with all doors closed and starting with the key in the off position, turn it to ON, OFF, ON, OFF, ON (don't turn the key to the start position just on) within 5 seconds and leave the key on and watch the digital odometer to see if it displays a fault code. It will be a P followed by 4 numbers example P0700. When it is done displaying codes or if there are no codes it will say done. If you can't get this to work, please try it again following the instructions!