"LOW DEF LEVEL" Indicator On Dash with Full DEF Tank

 At the Boston location today (06JUN2023) we discovered that a air bound or low aftertreatment fluid PSI will cause the "LOW DEF LEVEL" dash indicator and the low def red lamp on the gauge located on the tank AND Active Fault 1682 - Aftertreatment 1 Diesel Exhaust Fluid Dosing Unit Input Lines - Condition Exists this was cleared a few times but was still coming back as active during engine operation. The root cause of this was air in the system or potentially a dirty filter. The solution was to run the In-Chassis non-air flush procedure which requires CUMMINS INSITE, change the dosing injector and DEF Filter. The in chassis non-air flush procedure can be found in section 011-058 Aftertreatment Diesel Exhaust Fluid Dosing Unit of the service manual. We did not have the specified CUMMINS bottle setup, in result we utilized a 1/4" ID hose and a funnel to gravity feed the system as the test was running. A short way to isolate the suction side is to disconnect the DEF line to the dosing nozzle and place it in a bucket, then run the DEF Doser Pump Override Test via INSITE, if there is no fluid exiting the line then you know it is a suction issue at the pump or tank, in our case it was pump related and not debris located at the suction screen in the tank on the DEF header. As a result we were able to reprime the pump using the gravity feed, from this we reconnected the the suction line to the dosing fluid unit and kept the line to the dosing nozzle removed, we then ran the DEF Doser Pump Override Test and noticed at this time there was fluid coming out of the line, then, connected all necessary fittings and ran the DEF Doser Pump Override Test again monitoring the fluid pressures, it was SAT. To ensure all system were operating to specs we ran the Aftertreatment SCR System Test via INSITE, and everything came back SAT and all faults were cleared, at this time the "LOW DEF LEVEL" dash indicator had cleared and the red lamp on the gauge at the tank had cleared too. It is important to follow the CUMMINS troubleshooting tree to isolate issues instead of throwing parts at an application. In this troubleshooting procedure we replaced the DEF filter, and the dosing nozzle injector. The dosing nozzle assembly can be taken apart and the injector can be replaced individually, the injector can be found on Amazon, KM Sensors part number 0280158701. Stay tuned and we will post a video of the injector being removed and installed, this procedure will only cost $38.90 for the injector instead of $560 for the entire assembly from CUMMINS.