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 DEF quality sensor is typically mounted in the DEF tank or in-line with the DEF dosing unit supply line. Reference the OEM service manual for a detailed component location view.

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

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) lost communication with the aftertreatment DEF quality sensor via the J1939 data link.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.Engine torque will be reduced.Conditions for Clearing the Fault CodeThis fault code can not be cleared with INSITE™ electronic service tool.To validate the repair, start the engine and let it idle for up to 5 minutes.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.

Shop TalkPossible causes of this fault code include:

Open or short circuit on J1939 data link

Possible Cause:1) Loose Connections2) OEM harness3) ECM calibration