Cummins ISB4.5 CM2150 Fault Code: 3568 PID: SPN: 5394 FMI: 7 Aftertreatment Diesel Exhaust Fluid (DEF) Dosing Valve – Mechanical System Not Responding or Out of adjustment.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
The aftertreatment DEF dosing valve is controlled by the aftertreatment DEF controller. When the engine ECM commands DEF dosing, the DEF controller sends a pulse width modulated (PWM) signal to the dosing valve, which opens the dosing valve and allows DEF to be sprayed into the exhaust stream.

Component Location
The aftertreatment DEF dosing valve is installed in the exhaust system. It is mounted directly to the aftertreatment decomposition tube, before the Selective Catalytic Reduction (SCR) catalyst. Installation position will vary, based on the aftertreatment architecture and the OEM.

Conditions for Running the Diagnostics
This diagnostic runs when the DEF dosing valve is being commanded on.

Conditions for Setting the Fault Codes
The DEF controller has detected a mechanical malfunction of the DEF dosing valve.

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.
-An engine torque derate will be activated.

Conditions for Clearing the Fault Code
-This fault code can not be cleared with INSITE™ electronic service tool.
-To validate the repair, the DEF dosing valve must be commanded on in order for all diagnostics to run. This can be done by performing the Aftertreatment Diesel Exhaust Fluid (DEF) Doser Pump Override test in INSITE™ electronic service tool.
-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 the fault code is inactive.
-The inactive fault code will be cleared from the memory after 9600 hours of engine operation without a reccurrence.

Shop Talk
This fault detects a mechanical malfunction of the DEF dosing valve, or a pin-to-pin short in the DEF dosing valve circuit.

Contamination of the DEF can be a possible cause for this fault code.

Cummins ISB4.5 CM2150 Fault Code: 3567 PID: SPN: 5394 FMI: 5 Aftertreatment Diesel Exhaust Fluid Dosing Valve – Current Below Normal or Open Circuit.

Cummins ISB4.5 CM2150 Fault Code: 3566 PID: SPN: 5394 FMI: 4 Aftertreatment Diesel Exhaust Fluid Dosing Valve – Voltage Below Normal or Shorted to Low Source.

Cummins ISB4.5 CM2150 Fault Code: 3565 PID: SPN: 5394 FMI: 3 Aftertreatment Diesel Exhaust Fluid Dosing Valve – Voltage Above Normal or Shorted to High Source.

Cummins ISB4.5 CM2150 Fault Code: 3564 PID: SPN: 5491 FMI: 5 Aftertreatment Diesel Exhaust Fluid Line Heater Relay – Current Below Normal or Open Circuit.

Cummins ISB4.5 CM2150 Fault Code: 3563 PID: SPN: 5491 FMI: 4 Aftertreatment Diesel Exhaust Fluid Line Heater Relay – Voltage Below Normal or Shorted to Low Source.

Cummins ISB4.5 CM2150 Fault Code: 3562 PID: SPN: 5491 FMI: 3 Aftertreatment Diesel Exhaust Fluid Line Heater Relay – Voltage Above Normal or Shorted to High Source.

WARNING!