Cummins ISB4.5 CM2150 Fault Code: 3738 PID: SPN: 3489 FMI: 18 Air Supply Actuator – Data Valid But Below Normal Operating Range – Moderately Severe Level.

Circuit Description
The aftertreatment diesel exhaust fluid dosing unit air solenoid is used to enable and disable the truck air supply to the diesel exhaust fluid dosing unit. The air is used to transport the diesel exhaust fluid to the aftertreatment nozzle.

Component Location
The aftertreatment diesel exhaust fluid dosing unit air solenoid is mounted to the back of the diesel exhaust fluid dosing unit. The mounting location of the diesel exhaust fluid dosing unit is OEM specific.

Conditions for Running the Diagnostics
This diagnostic runs continuously while the Selective Catalytic Reduction (SCR) system is dosing diesel exhaust fluid into the aftertreatment system.

Conditions for Setting the Fault Codes
The dosing unit detects that the air supply has been lost while dosing diesel exhaust fluid into the aftertreatment system.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the MIL immediately after the diagnostic runs and fails.
-Engine torque will be reduced.

Conditions for Clearing the Fault Code
-This fault code can not be cleared with INSITE™ electronic service tool.
-To validate the repair, it is necessary to use INSITE™ electronic service tool to perform the Diesel Exhaust Fluid Doser Pump Override Test.
-Make sure that the diesel exhaust fluid dosing unit is able to successfully cycle through all phases (priming, dosing, and purging) and that diesel exhaust fluid flows evenly from the aftertreatment nozzle.
-The ECM will turn off the amber CHECK ENGINE lamp and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify that the fault code is inactive.
-The inactive fault code will be cleared from the memory after 9600 hours of engine operation without an occurrence again.

Possible Causes
-OEM air supply tubing damaged or leaking
-Malfunctioning air solenoid
-Malfunctioning aftertreatment diesel exhaust fluid dosing unit.