Q: shifter stuck in manual mode after accident

Without body damage, it is most likely a coincidence that it is stuck in manual mode. Regardless of how it came to quit working, it should be diagnosed just as any other failure would be.

I would begin with a wiring diagram and a test light. Study the diagram to get a feel for how the system is organized. Check all the fuses and take note of the fuses that power the shifter assembly. As I look at a wiring diagram for this system, I see a switch, which I’m sure your aware of, that is connected to what is called the "unified meter and A/C amp." At least this is what Mitchell calls this module. Regardless, check and make sure the switch is working by removing it and testing to see if it switches the ground path. If it does this, then things get quite a bit more complicated from here.

You will need a scanner to see if the module is relaying the switch information to the TCM (transmission control module). Most people don’t have access to a scanner that is advanced enough to do this. This is what needs to happen as all information beyond the simple switch grounding is done over the CAN (computer area network). If you need help having this looked at, a certified technician from YourMechanic can come to your home or office to diagnose your shifting issue and determine what fixes will resolve your issue.