The DTC code P0708 OBD2 is set at the moment the Powertrain Control Module (PCM) finds an out-of-range input voltage at the Transmission Range Sensor (TRS).
The TRS Sensor is a switch that rotates completing different circuits according to the position of the moving parts in the switch. Usually, the transmission selector shaft goes through the switch and moves the gear selector, the selector shaft rotates a moving part to complete the particular circuit.
The PCM or TCM uses the TRS Sensor to know the position of the shift lever. If signals are indicating two different shift positions at the same time for more than 30 seconds, this code will be set. If this occurs twice in a row, the Check Engine light illuminates and the transmission is instructed to enter the fail-safe mode.