Cummins ISB4.5 CM2150 Fault Code: 3151 PID: SPN: 4794 FMI: 31 Aftertreatment SCR Catalyst System Missing – Condition Exists.

Circuit Description
The aftertreatment selective catalytic reduction (SCR) catalyst is monitored by SCR intake and SCR outlet temperature sensors that are located in the aftertreatment system. The intake temperature sensor is located before the catalyst and the outlet temperature sensor is located at the outlet of the catalyst system.

Component Location
The SCR catalyst is located in the exhaust system. The location of the SCR catalyst can vary depending on the original equipment manufacturer (OEM). Refer to the OEM service manual for detailed engine and component identification.

Conditions for Running the Diagnostics
The engine must be turned OFF for period of 8 hours before this diagnostic will run. This diagnostic runs when the keyswitch is turned to the ON position after an 8 hour cold soak. The SCR catalyst intake and outlet temperature sensors must be reading ambient temperature. If the SCR catalyst temperature is above 38°C [100°F], or the SCR catalyst temperature sensors have a difference of more than 5.5°C or 10°F, the diagnostics will not run.

Conditions for Setting the Fault Codes
This fault code becomes active when the SCR intake and outlet temperature sensors do not detect the presence of an SCR catalyst in the aftertreatment system.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (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, refer to the “Conditions for Running the Diagnostic” section for instructions on running the diagnostic.
-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 reoccurrence.

Possible Causes
-Incorrect calibration revision on INCAL™ CD
-Tampering with the catalyst system, removal of the catalyst from vehicle, or a malfunctioning catalyst