TROUBLESHOOTING
CODES

DEF (Diesel Exhaust Fluid) or DPF (Diesel Particulate Filter) systems codes:

1. **SPN 3226 FMI 13** - indicates an issue with the SCR (Selective Catalytic Reduction) outlet NOx sensor, where the signal from the part is unavailable. The SCR system is closely related to DEF usage.

2. **SPN 3250 FMI 0** - relates to the DOC (Diesel Oxidation Catalyst) outlet temperature being very high, which could affect the DPF regeneration process or indicate a problem within the exhaust aftertreatment system.

3. **SPN 1761 FMI 9** - points to a problem with the DEF Fluid Level, specifically an abnormal update rate, which could lead to DEF system faults if not addressed.

4. **SPN 4792** - directly relates to the Aftertreatment 1 Diesel Particulate Filter Ash Load Percent, indicating when the DPF might need servicing due to ash accumulation, which affects its efficiency and could lead to regeneration issues.

5. **SPN 3719 FMI 9** - associated with Aftertreatment 1 Outlet NOx, which could be related to DEF system performance or SCR catalyst efficiency.

6. **SPN 4094 FMI 3** - indicates NOx Limits Exceeded, which might be due to issues in the DEF system or SCR catalyst not functioning correctly.

7. **SPN 4334 FMI 18** - refers to extremely low DEF consumption, which might suggest a problem with DEF delivery or injection, or an issue with the DEF system not functioning as intended.

8. **SPN 5394 FMI 0** - aftertreatment 1 Outlet NOx Sensor Reading Extremely High, which could be due to problems in the DEF system or the SCR not reducing NOx effectively.

These codes highlight issues within the DEF and DPF systems, which are critical for modern diesel engines to meet emission standards. They cover a range from DEF level issues, NOx sensor problems, to DPF ash loading, all of which are integral to the proper functioning of a truck's emission control systems. Remember, these codes might not directly appear in the exact format in your truck's

 

 

 

DEF (Diesel Exhaust Fluid) or DPF (Diesel Particulate Filter) systems that might lead to engine derate or limit engine performance:

1. **SPN 4094 FMI 3** - indicates NOx Limits Exceeded, which could be due to issues in the DEF system or SCR (Selective Catalytic Reduction) catalyst not functioning correctly, potentially leading to derate for emission compliance.

2. **SPN 5394 FMI 0** - aftertreatment 1 Outlet NOx Sensor Reading Extremely High, suggesting a problem with NOx levels which might trigger derate to enforce emission control.

3. **SPN 1761 FMI 9** - points to a problem with the DEF Fluid Level, specifically an abnormal update rate. If the DEF system detects low fluid or a malfunction, it can lead to engine derate.

4. **SPN 4334 FMI 18** - refers to extremely low DEF consumption, which might suggest a problem with DEF delivery or injection, or an issue with the DEF system not functioning as intended, potentially resulting in derate.

5. **SPN 5246 FMI 0** - often relates to the Diesel Particulate Filter (DPF) Differential Pressure Sensor, which, if indicating high differential pressure, could trigger a derate to force a regeneration or maintenance.

These codes are critical because they relate to the emission control systems of modern diesel engines. If these systems detect issues that could lead to non-compliance with emission standards, the engine control module (ECM) might derate the engine or limit its performance to enforce maintenance or correction of the issue. Remember, these codes might not directly appear in the exact format in your truck's diagnostic system, but they represent common issues that could lead to derate or performance limits due to DEF or DPF system problems.