You are correct that this is a transmission issue. The PRNDL lights flashing means there is a serious fault with the system and it is shifting to neutral to protect itself.
There are two options. Have it checked out by a shop or get the codes out of the computer and hopefully it is just a sensor issue.
Let me know if you can get the codes and we can go from there or the results of what a shop finds out. Thanks
Thursday, July 11th, 2019 AT 6:01 PM