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 tank heater control valve is located near the diesel exhaust fluid tank. Specific location will vary depending on the vehicle OEM. The tank heating coil is internal to the diesel exhaust fluid 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 aftertreatment diesel exhaust fluid tank heater was commanded on by the engine engine control module (ECM), but no corresponding temperature increase in the aftertreatment diesel exhaust fluid tank temperature was recorded by the tank temperature sensor.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

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 restrictions in the coolant plumbing to the diesel exhaust fluid tank heaterEngine coolant level lowMalfunctioning aftertreatment diesel exhaust fluid tank heater control valveReference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Cause:1) Coolant level2) DEF tank heater control valve failure3) ECM calibration