Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control): Notes

The reductant system supplies the Selective Catalyst Reduction (SCR) stage of the vehicle's exhaust aftertreatment system with the Diesel Exhaust Fluid (DEF) required to reduce exhaust Oxides of Nitrogen (NOx) levels. The Engine Control Module (ECM) continuously monitors the performance of the emission system during operation

When the conditions associated with a fault in the emission system operation are detected, the ECM activates the emission control feature and presents the driver with a series of prompts and warnings.

Once initiated, emission control warnings grow increasingly more serious as the vehicle continues to be driven. The vehicle's current warning status is not displayed on the scan tool. The series emission control warnings alert the driver that EGR/SCR system service is urgently needed.