Cummins ISB4.5 CM2150 Fault Code: 3237 PID: SID 254 SPN: 4340 FMI: 3 Aftertreatment Diesel Exhaust Fluid Line Heater 1 Circuit – Voltage Above Normal or Shorted to High Source.

Circuit Description
The aftertreatment diesel exhaust fluid line heater 1 is controlled by the ECM, and receives power through the switch side of the diesel exhaust fluid line heater relay.

Component Location
The aftertreatment diesel exhaust fluid line heater 1 is located on the supply line between the diesel exhaust fluid dosing unit and the aftertreatment nozzle.

Conditions for Running the Diagnostics
This diagnostic runs when the keyswitch is in the ON position and the heater is commanded on.

Conditions for Setting the Fault Codes
The ECM detects that the line heater voltage is above a calibratible value.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails
-The line heater will be disabled.

Conditions for Clearing the Fault Code
-Upon completion of the repair, the heater must be commanded on for the diagnostic to run and the fault to go inactive
-Use the INSITE™ electronic service tool to perform the “Diesel Exhaust Fluid Doser System Heater Test” found under “ECM Diagnostic Tests”.
-The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

Possible Causes
-Malfunctioning line heater
-Short circuit to battery in the OEM wiring harness
-Malfunctioning ECM.