Cummins ISB4.5 CM2150 Fault Code: 3149 PID: SID 254 SPN: 4363 FMI: 10 Aftertreatment SCR Outlet Temperature Sensor – Abnormal Rate of Change.

Circuit Description
The SCR catalyst outlet temperature sensor is used by the electronic control module (ECM) to monitor the engine exhaust temperature entering the catalyst unit. The ECM monitors the voltage on the signal pin and converts this to a temperature value.

Component Location
The SCR catalyst outlet temperature sensor is located in the aftertreatment system. It is located in the outlet of the SCR catalyst unit.

Conditions for Running the Diagnostics
The engine and keyswitch must be turned off for period of 8 hours before this diagnostic will run. This diagnostic will only run during engine warm up. After an 8 hour cold soak, start and operate the engine until the normal operating temperatures are reached.

Conditions for Setting the Fault Codes
The ECM detects that the SCR catalyst outlet temperature is not changing to match engine operating conditions.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light and/or the MIL immediately when the diagnostic runs and fails.
-An engine torque derate will be activated after 36 hours of engine operation with the fault code active.

Conditions for Clearing the Fault Code
-This fault code can not be cleared with INSITE™ electronic service tool.
-The ECM will turn off the amber CHECK ENGINE light and/or MIL immediately after the diagnostic runs and passes.
-Refer to the “Conditions for Running the Diagnostic” section for instructions on running the diagnostic.
-Use INSITE™ electronic service tool to verify the fault code is inactive.
-The inactive fault code will be cleared from memory after the completion of 40 warm-up cycles.

Shop Talk
The SCR catalyst outlet temperature sensor is monitored during engine warm-up. If the SCR catalyst outlet temperature reading is not changing to match the engine operating conditions, the SCR catalyst outlet temperature sensor is then determined to be stuck in-range and this fault code is logged.

Possible Causes
-Stuck in-range SCR catalyst outlet temperature sensor reading
-High resistance in the SCR catalyst outlet temperature sensor signal or return lines.