Lamp:Red

Reason:Unknown fluid inside DEF tank.

Effect:Engine power derate.

Circuit Description:The aftertreatment Diesel Exhaust Fluid (DEF) sensor is a smart device that communicates to the ECM via the J1939 datalink. The aftertreatment DEF sensor performs its own internal diagnostics and reports malfunctions back to the primary Engine Control Module via the J1939 datalink. The aftertreatment DEF sensor monitors the tank level, temperature and quality of the DEF fluid.

Component Location:The aftertreatment diesel exhaust fluid (DEF) sensor is located in the aftertreatment DEF tank. Location of the tank and sensor is OEM dependent.

Conditions for Running the Diagnostics:This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Code:The Engine Control Module (ECM) detected the aftertreatment diesel exhaust fluid quality sensor reported an unknown error.

Action Taken When the Fault Code is Active:The ECM illuminates the red stop engine lamp immediately after the diagnostic runs and fails.

Conditions for Clearing the Fault Code:1. The ECM will turn off the red stop engine lamp immediately after the diagnostic runs and passes.2. The fault code status displayed by the recommended diagnostic tool or equivalent will change to inactive immediately after the diagnostic runs and passes.

Shop Talk:Possible causes of this fault code include:1. Damaged sensor.2. Degraded, diluted, or incorrect diesel exhaust fluid.