Theory Of Operation
WARNING: This page is about a different car, the 2016 RAM 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The Transmission Range Switch (TRS) is located in the Transmission. When the driver selects a gear position, the Shifter is moved, which actuates a cable that is connected to the TRS. The TRS contains several switches. These switches are OPEN or CLOSED depending on the intended gear position. Normally, at least one TRS Sense circuit switch is OPEN. If the TCM detects that all of the switches are CLOSED, a DTC is set. If the driver leans on the shift lever, forcing it into what is called the Over-Travel position, this will make all of the TRS Sense circuit switches CLOSED.
When the TRS sense circuit detects a high voltage condition, it is considered CLOSED. When a TRS sense circuit detects a low voltage condition, it is considered OPEN.