A transmission range sensor, or TRS, sometimes referred to as a neutral safety switch, is a safety device and sensor that, when faulty, prevents the car from starting unless it is in neutral or park. Failure of this part is generally common among older, high-mileage vehicles as the sensor becomes exposed to the weather and various elements.
The TRS often displays an error code, P0705, when it is faulty. This may occur when the vehicle is in motion yet the TRS signal suggests that the vehicle is in park while the speed sensor indicates that the vehicle is moving. The sensor portion of the TRS indicates to the vehicle's Powertrain Control Module, PCM, what gear the vehicle is currently in when the key is turned to the on position or the engine is started.