In this design, when the system shuts down, the DEF just goes back to the tank by gravity and depressurizes over time, but every DEF pump I have seen recently indeed has a brushless DC motor. The other design I have seen (which seems to be common in many aftertreatment systems) is one having a pump without check valves. Depending on the model, some will have a pressure sensor built internally to monitor pressure and will have valves in the pump to redirect flow during a purge cycle. These electronic-controlled pumps need digital signals to work.
These DEF pumps are not your average DC electric motors anymore (ones containing brushes/commutator that are energized through a switch). This method is much faster than doing all the resistance checks the manufacturer wants you to do on the harness, according to service information. In this article, I am going to show you how to diagnose a faulty DEF pump with a scope. We understand the theory of how the pump is supposed to work, but how do we diagnose a DEF pump problem? Within the chamber, a chemical reaction takes place, and the result is a reduction in oxides of nitrogen (NOx). They are used to supply pressurized fluid to the doser injector, so it can deliver the fluid in an atomized spray into the selective catalyst reduction (SCR) chamber. As everyone knows Diesel Exhaust Fluid (DEF) Pumps are now in use on every aftertreatment system out there today on the modern heavy-duty vehicle.
I think this month’s case study will have HD techs very interested.
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