Circuit DescriptionThe DEF quality sensor is a smart device and communicates with the engine electronic control module (ECM) via the J1939 data link. The DEF quality sensor receives power and ground directly from the battery. The sensor performs its own internal diagnostics and reports malfunctions back to the primary engine ECM via the J1939 data link. The DEF quality sensor is used to measure the concentration of the DEF in the tank.

Component LocationThe aftertreatment diesel exhaust fluid quality sensor is located in the aftertreatment diesel exhaust fluid tank. It may be a combination sensor with the aftertreatement diesel exhaust fluid tank level and tank temperature sensors. Location of the tank and sensor is OEM dependent. Refer to the OEM service manual.

Conditions for Running the DiagnosticsThe diagnostic runs continuously when the following conditions are met:

Keyswitch is in the ON position or when the engine is running.Ambient temperature is above -20°C [-4°F].Vehicle altitude change is less than 305 m [1000 ft] in 1 hour.Conditions for Setting the Fault CodesThe DEF quality sensor has detected that the DEF concentration has fallen below a critical threshold.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.Diesel exhaust fluid injection into the aftertreatment system is disabled.Conditions for Clearing the Fault CodeTo validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop TalkPossible causes of this fault code include:

Degraded, diluted, or incorrect diesel exhaust fluidMalfunctioning Aftertreatment DEF Quality Sensor.

Possible Cause:1) DEF fluid2) ECM calibration