Reductant Pump Assembly

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The reductant pump assembly contains a rotary vane pump, a pressure sensor, a temperature sensor, and an internal heating element.

The reductant pressure sensor provides feedback to the PCM, which regulates system pressure by controlling pump speed using PWM signals to the reductant pump control module.

The reductant temperature sensor is a thermistor device which provides feedback to the PCM, which controls the reductant heaters to keep the reductant in a liquid state during low ambient temperatures. The reductant temperature sensor is integral to the reductant pump assembly.

When the PCM requests reductant injection, the reductant injector opens and the pump operates, filling the reductant pressure line and injector and purging air from the system. When all air is purged, the injector closes and the pump builds pressure. The system is then primed and the injector provides DEF (diesel exhaust fluid) to the SCR as commanded by the PCM.

When the vehicle is shut down, the PCM closes the injector and reverses the pump direction, causing the pump to reverse flow and bleed down pressure on the reductant pressure line. The PCM then opens the injector to allow gas to enter the reductant pressure line, which in turn allows the pump to purge all remaining DEF from the system and return it to the reductant tank. The PCM closes the injector and shuts down the reductant pump.

The PCM commands the GPCM (glow plug control module) to provide voltage to the reductant pump assembly internal heating element when the reductant temperature approaches -11 deg.C (12 deg.F).