Cummins X15 CM2450 X124B (2018 & Newer) Fault Code: 4156 PID: SPN: 5746 FMI: 4 Aftertreatment 1 Diesel Exhaust Fluid Dosing Unit Heater Relay Circuit- Voltage Below Normal or Shorted to Low Source

Circuit Description
The aftertreatment diesel exhaust fluid dosing unit heater relay is used to provide power to the aftertreatment diesel exhaust fluid dosing unit heater.

The aftertreatment diesel exhaust fluid dosing unit heater is used to defrost and/or prevent freezing of the diesel exhaust fluid dosing unit.

Component Location
The aftertreatment diesel exhaust fluid dosing unit heater relay is an OEM component. Refer to the OEM service manual for component location.

Conditions for Running the Diagnostics
This diagnostic runs when the aftertreatment diesel exhaust fluid dosing unit heater is commanded OFF.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the aftertreatment diesel exhaust fluid dosing unit heater relay signal was out of range low.

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.
Diesel exhaust fluid injection into the aftertreatment system is disabled.
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 Code
To 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 Talk
Possible causes of this fault code include:

A malfunctioning aftertreatment diesel exhaust fluid dosing unit heater relay
A short circuit to ground in the OEM harness
An open circuit in the OEM harness

Possible Cause:
1) OEM harness
2) ECM calibration