Theory Of Operation

The Diesel Exhaust Fluid (DEF) Tank Level Sensor and Diesel Exhaust Fluid (DEF) Tank Temperature Sensor are to measure the level and temperature of the fluid inside the DEF Tank. Though integrated with the DEF Supply Pump the level sensor and the temperature sensor operate independently. The temperature sensor operates as a typical two wire 5-Volt sensor. The level sensor operates as a typical three wire 5-Volt sensor. The DEF Tank Temperature Sensor is a negative temperature coefficient sensor. The sensors are not sold separately and must be replaced with the DEF Supply Pump assembly. The DEF Dosing Control Unit will illuminate the MIL lamp via the Powertrain Control Module (PCM) after this diagnostic runs and fails for two consecutive trips. The DEF Dosing Control Unit will turn off the MIL lamp via the PCM immediately after the diagnostic runs and passes. Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.