A 2016 Detroit DD15 engine with 693,000 miles experienced a sudden derate, accompanied by diagnostic trouble codes (DTCs) SPN 4364 FMI 18 and SPN 5246 Fmi 0. The engine derate limited speed to 5 mph and displayed warning lights, including a red stop engine light and a flashing DEF light. This article explores the possible causes and solutions related to SPN 5246 FMI 0.
SPN 5246 FMI 0: Decoding the Diagnostic Trouble Code
SPN 5246 FMI 0 points to an issue with the Diesel Exhaust Fluid (DEF) system. Specifically, FMI 0 indicates a data valid but above normal operating range. This suggests that the DEF system is detecting a problem, potentially related to DEF quality, DEF level, or a sensor malfunction within the system. While the original error message indicated “DEF Quality Poor,” further investigation is necessary to pinpoint the root cause.
Possible Causes of SPN 5246 FMI 0
Several factors can contribute to SPN 5246 FMI 0 in a Detroit DD15 engine:
- Contaminated DEF: Poor quality or contaminated DEF can disrupt the SCR system and trigger the fault code.
- Low DEF Level: Insufficient DEF in the tank can lead to a derate. While unlikely given the “DEF Quality Poor” message, it’s worth checking.
- DEF Sensor Issues: A faulty DEF level sensor, temperature sensor, or quality sensor can provide incorrect readings, activating the code.
- DEF Line Restrictions: Blockages or restrictions in the DEF lines can hinder proper flow and cause problems.
- SCR System Malfunction: Issues within the Selective Catalytic Reduction (SCR) system itself, such as a faulty injector or catalyst, can contribute to the error.
Troubleshooting SPN 5246 FMI 0
Given the previous DEF system cleaning and the recurring nature of the issue, a more thorough diagnosis is required. While cleaning the DEF injector was a good first step, it didn’t resolve the problem. The following steps are recommended:
- Check DEF Quality: Test the DEF fluid to ensure it meets ISO 22241 standards.
- Inspect DEF System Components: Thoroughly examine the entire DEF system, including the tank, pump, lines, injector, and sensors, for any signs of damage, leaks, or contamination.
- Diagnose with Diagnostic Software: Use specialized diagnostic software to access more detailed information from the engine control module (ECM) and pinpoint the specific fault within the DEF system. This will likely provide more specific data related to SPN 5246 FMI 0.
- Consult a Qualified Technician: If the problem persists, consult a qualified diesel technician with experience in Detroit DD15 engines and aftertreatment systems.
Conclusion: Addressing DEF System Issues in Detroit DD15 Engines
SPN 5246 FMI 0 indicates a problem within the DEF system of a Detroit DD15 engine. While the temporary resolution by driving downhill at higher speeds suggests a possible intermittent connection or sensor glitch, it’s crucial to address the underlying issue to prevent further derates and potential damage to the aftertreatment system. A comprehensive diagnostic approach is necessary to identify the root cause and implement the appropriate repairs. Ignoring this code could lead to costly repairs and downtime in the future.
