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 continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault CodesThe diesel exhaust fluid controller detected the diesel exhaust fluid tank heater circuit was open.

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.Diesel exhaust fluid tank heating will be disabled.Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.Engine torque will be severely reduced.Vehicle speed will be limited to 8 km [5 mi] per hour after extended engine operation with the fault code active.

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.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 TalkThe aftertreatment diesel exhaust fluid tank heater control valve may be powered by an OEM supplied power relay, which is connected to the aftertreatment diesel exhaust fluid controller harness. When troubleshooting wiring harness issues, it may be necessary to include the optional line heater relay.

Possible causes of this fault code include:

Open circuit in the aftertreatment diesel exhaust fluid controller harnessMalfunctioning aftertreatment diesel exhaust fluid tank heater control valveMalfunctioning aftertreatment diesel exhaust fluid controller.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink 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) ECM calibration