Cummins ISX15 CM2250 (2010-12) Fault Code: 3151 (HD) PID: SPN: 4364 FMI: 18 Aftertreatment SCR catalyst Conversion Efficiency- Data Valid But Below Normal Operating Range- Moderately Severe Level

Circuit Description
The engine control module (ECM) monitors the mono-nitrogen oxides (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 selective catalystic reduction (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. NOx sensor data is gathered over varying engine speeds and loads. When enough data has been gathered, the diagnostic will run, make a pass/fail decision, and begin to gather data again.

Conditions for Setting the Fault Codes
The ECM detects that the NOx conversion across the SCR catalyst is lower than expected.

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.
Conditions for Clearing the Fault Code
To validate repairs that utilized the Dynamic Engine Systems Analysis tool during the troubleshooting process, re-run the Dynamic Engine Systems Analysis test. Do not perform a stationary regeneration. When the Dynamic Engine System Analysis Test results all pass the repair has been validated.
To validate repairs that did not utilize the Dynamic Engine Systems Analysis tool during the troubleshooting process, perform a stationary regeneration. After completing a stationary regeneration (as instructed in this fault code troubleshooting tree) and no additional faults become active, the repair has been validated.
NOTE: This fault code will still be active.

It is necessary to use the “Reset All Faults” command in INSITE? electronic service tool to clear this fault and turn off the amber CHECK ENGINE lamp and/or MIL.

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

Possible causes of this fault code include:

Malfunctioning diesel exhaust fluid (DEF) dosing system
Exhaust system leaks
Malfunctioning SCR catalyst
Degraded, diluted, or incorrect DEF
Diesel exhaust fluid deposits in decomposition tube.
This fault code can be set as a result of multiple failure modes. All steps of the troubleshooting tree must be completed.

Possible Cause:
1) Aftertreatment DEF dosing unit filter failure
2) ECM calibration