Cummins ISB4.5 CM2150 Fault Code: 3612 PID: SPN: 3361 FMI: 7 Aftertreatment Diesel Exhaust Fluid Dosing Unit – Mechanical System Not Responding or Out of Adjustment.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
The diesel exhaust fluid dosing unit performs many functions, one of which is to generate adequate diesel exhaust fluid pressure in the lines using a pump to allow for dosing. The diesel exhaust fluid controller provides a battery voltage supply and a ground to the diesel exhaust fluid dosing unit. The controller also supplies a signal to the dosing unit to control the diesel exhaust fluid output. This signal changes based on the diesel exhaust fluid pressure being commanded.

Component Location
The aftertreatment diesel exhaust fluid dosing unit location is OEM dependent. Refer to the OEM service manual for more information.

Conditions for Running the Diagnostics
This diagnostic runs at initial key ON.

Conditions for Setting the Fault Codes
The aftertreatment diesel exhaust fluid controller detects that an incomplete powerdown purge cycle has occurred.

Action Taken When the Fault Code is Active
The fault code will be set active immediately when the diagnostic runs and fails. This is a no-lamp fault.

Conditions for Clearing the Fault Code
-This fault code will go inactive upon successful completion of a powerdown and purge cycle of the SCR dosing system.
-This fault code can also be cleared with INSITE™ electronic service tool.

Shop Talk
The SCR system is programmed to automatically purge itself after the engine has shut down. Immediately following key OFF, the diesel exhuast fluid (DEF) return valve will be actuated and the dosing unit will pump any DEF left in the lines and dosing unit back to the DEF tank. The purge cycle can take up to 60 Seconds.

This is an information only fault code that indicates that something is not allowing the diesel exhaust fluid dosing unit to fully complete its purge cycle. Failure to complete the purge cycle could lead to deposits forming in the diesel exhaust fluid system or damage to the dosing unit caused by freezing of the diesel exhaust fluid. Make sure the battery power is not being removed from the SCR system immediately after engine shutdown via a main battery disconnect switch.

Cummins ISB4.5 CM2150 Fault Code: 3598 PID: SPN: 3360 FMI: 19 Aftertreatment Diesel Exhaust Fluid Controller – Received Network Data In Error.

Cummins ISB4.5 CM2150 Fault Code: 3597 PID: SID 254 SPN: 3360 FMI: 9 Aftertreatment Diesel Exhaust Fluid Controller – Abnormal Update Rate.

Cummins ISB4.5 CM2150 Fault Code: 3596 PID: SPN: 4334 FMI: 2 Aftertreatment Diesel Exhaust Fluid Pressure Sensor – Data Erratic, Intermittent, or Incorrect.

Cummins ISB4.5 CM2150 Fault Code: 3579 PID: SPN: 4376 FMI: 5 Aftertreatment Diesel Exhaust Fluid Return Valve – Current Below Normal or Open Circuit.

Cummins ISB4.5 CM2150 Fault Code: 3578 PID: SPN: 4376 FMI: 4 Aftertreatment Diesel Exhaust Fluid Return Valve – Voltage Below Normal or Shorted to Low Source.

Cummins ISB4.5 CM2150 Fault Code: 3577 PID: SPN: 4376 FMI: 3 Aftertreatment Diesel Exhaust Fluid Return Valve – Voltage Above Normal or Shorted to High Source.

WARNING!