This SCR temperature sensor monitors exhaust-gas temperature in the selective catalytic reduction system of the host tractor or vehicle. It sits in the exhaust stream downstream of the diesel oxidation catalyst and upstream of the SCR catalyst, providing the engine control unit with a temperature signal used to regulate urea dosing. A failed or inaccurate sensor can cause the SCR system to enter a derated or fault-limited operating mode, reducing engine power and increasing fuel consumption. The sensor is built to the original manufacturer's calibration curve, so its resistance-versus-temperature response matches the ECU's lookup table without recalibration. On installation, ensure the connector is fully seated and the wiring harness is routed away from sharp edges and heat sources.