Cummins ISX12 CM2250 (2010-12) Fault Code: 3151 PID: SPN: 4794 FMI: 31 Aftertreatment 1 SCR Catalyst System Missing- Condition Exists - EcuForce Truck (2024)

Circuit Description
The engine control module (ECM) monitors the NOx concentration in the engine’s exhaust gases using an aftertreatment intake NOx sensor and an aftertreatment outlet NOx sensor. By comparing these two values, the ECM is able to determine the conversion efficiency of the SCR catalyst and dosing system.

Component Location
The SCR catalyst is located in the vehicle’s exhaust system, after the diesel particulate filter and decomposition tube.

Conditions for Running the Diagnostics
This diagnostic has to meet specific engine and aftertreatment conditions to run and complete.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the NOx conversion efficiency of the SCR catalyst was critically low.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

Diesel exhaust fluid injection into the aftertreatment system is disabled.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Engine torque will be severely reduced.
Vehicle speed will be limited to 8 km [5 mi] per hour after extended engine operation with the fault code active.

Conditions for Clearing the Fault Code
After completing a stationary regeneration (as instructed in this fault code troubleshooting tree) and no additional faults become active, the repair has been validated.

It is necessary to use the “Reset All Faults” command in INSITE? electronic service tool to clear this fault and extinguish the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL).

Shop Talk
Troubleshoot all other active NOx sensor and SCR dosing system related fault codes before this fault.

Possible causes of this fault include:

Incorrect calibration revision on INCAL? CD
Tampering with SCR catalyst system, removal of SCR catalyst from vehicle, or malfunctioning SCR catalyst
Malfunctioning diesel exhaust fluid dosing system
Exhaust system leaks
Degraded, diluted, or incorrect diesel exhaust fluid
Diesel exhaust fluid deposits in the decomposition tube.
For unit that has come back into with repeat failures consider the possibility that customer is not using Ultra-low sulfur Diesel fuel
This fault code can be set as a result of multiple failure modes. All steps of the troubleshooting tree must be completed.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:
1) N/A

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