This diagnostic function starts monitoring the DEF dosing pressure when the DEF pump is set to ?Running? mode. The aftertreatment control module (ACM) keeps track of the time when the pump is not in the ?Running? mode. When the time that the pump is not in “Running” mode accumulates to more than 25 % of a predetermined amount of time a DTC will set.

Conditions for diagnostic trouble code (DTC):
1) Dosing failure

Observable symptoms
1) Leakage, pressure side

Probable cause
1) Low fluid level in the tank
2) Leakage from hoses or connections
3) Aftertreatment Diesel Exhaust Fluid (DEF) Return Valve
4) Aftertreatment line connections swapped

Detailed information
1) If the DEF dosing pressure drops but can be built up again and dosing is interrupted for too long of period time this DTC is set