Circuit DescriptionThe 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 LocationThe aftertreatment diesel exhaust fluid (DEF) sensor is located in the aftertreatment DEF tank. Location of the tank and sensor is OEM dependent. Refer to the OEM service manual.

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

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the aftertreatment diesel exhaust fluid tank temperature signal voltage was out of range high.

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 fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp 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:

Malfunctioning DEF Quality Sensor

Possible Cause:1) Aftertreatment DEF quality sensor failure2) ECM calibration