Car goes into limp mode (wont go or stop) once wrench symbol pops up (no check engine light). I've gotten 2 diagnostic's and they've found nothing wrong. Car has had an oil change and transmission fluid within the past 2 weeks.

 

I don't know why it won't go or stop in limp mode. It should drive very slowly, but drive and stop. I suspect the sensor in the instrument cluster is faulty. It'd help giving yr make model.
Vehicles that have adjustable maintenance reminders sually have a screen that you can adjust the milage. If so, have you reset it? Something in computer could do that. A parts shop diagnostic may not have the ability to check those parameters. It may need to go to a factory \ dealer to have that checked.