Theory Of Operation
WARNING: This page is about a different car, the 2014 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
The Diesel Exhaust Fluid (DEF) Tank Level Sensor and Diesel Exhaust Fluid (DEF) Tank Temperature Sensor are combined in one circuit to measure the level and temperature of the fluid inside the DEF Tank. This circuit is used to transmit a multiplexed PWM signal from the DEF Tank to the Powertrain Control Module (PCM). This one circuit carries three pieces of information: The DEF Tank level (Measured by using an ultrasonic transducer reporting ultrasound waves reflected/echoed by the fluid surface), the DEF temperature, and the DEF Level/Temperature Sensor status.