Will a bad torque converter cause my car to not go into gear?

Hello, "won't touch it unless there's a code" - I would suggest engaging with the service manager at the dealership. And, you can go further than that. If you are having a problem, sometimes codes don't set. It may be up to you to demonstrate the concern to a technician - no matter where you take the vehicle. But since warranty is in effect still, likely, I would definitely suggest pursuing getting further assistance. What leads you to thinking there's a problem with the torque converter? I don't see any likely correlation to the concern. Try another dealership perhaps or seek guidance with management for help.