Red Line/RPM Monitor for Type-S

Hello All,

This is my first post, so please forgive any formalities I miss. I am currently working on a project for an Electronics class at NC State. For this project, I am making a HUD (heads up display) with speed and a Red Line monitor for my 2008 TL Type-S. I have to do this using an Arduino Uno. I have purchased an OBD-II adapter, and with it comes a superfluous library with everything I would need, including code to light an LED if RPMs exceed 3000. So far, I have managed to get it to work, but only on my roommates 2010-ish scion Tc, and my neighbors 2005 Mazda 3. The OBD-II adapter refuses to read in my car.
I have traveled to the dealership and they tested the OBD-II port to make sure it was working. (it was)
I'm curious if anyone has worked on a project similar to this, and if so, any ideas why the OBD-II adapter isn't working for my car.
As mentioned, it is a 2008 TL Type-S and it has a manual transmission.
(which probably doesn't matter, but the more info the better)
The OBD-II adapter comes from:
OBD-II Adapter for Arduino - Model A (UART)
It is the Model A version with UART protocol