Circuit DescriptionThe aftertreatment diesel exhaust fluid tank heater keeps the diesel exhaust fluid from freezing in the diesel exhaust fluid tank. The tank heater consists of an electrically powered tank heater control valve which controls the flow of engine coolant to a heating coil inside the diesel exhaust fluid tank. The tank heater control valve opens to allow coolant to flow to the heating coil when heating is commanded, and closes when heating is no longer required.

Component LocationThe diesel exhaust fluid (DEF) tank heater control valve is installed on the coolant supply line located near the DEF tank. Specific locations will vary depending on the OEM.

The diesel exhaust fluid (DEF) tank heating coil is internal to the DEF tank.

Conditions for Running the DiagnosticsThis diagnostic runs a calibrated amount of time after diesel exhaust fluid tank heating is first commanded.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the aftertreatment diesel exhaust fluid tank temperature failed to thaw after the aftertreatment diesel exhaust fluid tank heater was commanded on for a calibratable time.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault CodeThe fault code status in INSITE? electronic service tool will change to INACTIVE immediately after the system is able to adequately heat and the diagnostic runs and passes. If heating can not be completed, use the “Diesel Exhaust Fluid Doser System Heater Test” found under “ECM Diagnostic Test” in INSITE? electronic service tool to command heating to the tank heater and all line heaters.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where 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:

Aftertreatment diesel exhaust fluid tank heater control valve stuck closedBlockage or restrictons in the coolant plumbing to the diesel exhaust fluid tank heaterEngine coolant level lowMalfunctioning aftertreatment diesel exhaust fluid tank heater control valveMalfunctioning aftertreatment diesel exhaust fluid controller is unable to command tank heating.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and data link communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible cause:1) DEF tank Heater control valve failure2) ECM calibration