A 2017 Detroit DD15 engine is experiencing persistent issues with low NOx conversion efficiency, likely related to fault code 4364 17. Despite numerous repairs and component replacements, the problem persists. This article outlines the troubleshooting steps taken so far and explores potential solutions for this complex issue.
Troubleshooting Steps Undertaken
The initial diagnosis at a dealership pointed towards a faulty outlet NOx sensor and required module updates. However, replacing the sensor and updating the modules did not resolve the issue. Subsequent attempts included valve adjustments, air filter and air filter box replacement, and even a suggested One Box replacement.
Unsatisfied with the dealership’s findings, the owner took matters into their own hands. The following steps were performed:
- DEF System: The DEF fluid was replaced and tested. The Delta pressure sensor, MAF sensor, air intake temperature sensor, and HC doser were replaced due to soot contamination.
- DPF and One Box: The DPF filters (two of which were new) and the One Box were cleaned. A new inlet NOx sensor, inlet DOC pressure sensor, hose (previously clogged), and soot sensor were installed. A regen was performed after these steps.
- Other Components: A new DEF doser and DOC face plug were installed. A leaking variable water pump and thermostat were also replaced due to fluctuating engine temperatures.
Despite these extensive efforts, the NOx conversion efficiency remains erratic, fluctuating between 95-100% and dropping to 0% or below 60%. The DOC inlet pressure reads 0.4-0.6, while the outlet DOC pressure is half that value. The inlet NOx is around 400 ppm, and the outlet NOx sometimes exceeds the inlet value. No DEF crystallization is present. The wiring harness from the ACM to the sensors appears undamaged, and ohm readings from the ACM to the outlet NOx sensor are within the acceptable range.
Potential Causes of Fault Code 4364 17
The intermittent nature of the problem suggests a potential issue that is triggered by temperature changes, as the NOx efficiency seems to decrease as the engine heats up. Possible causes include:
- Faulty ACM (Aftertreatment Control Module): The ACM might be malfunctioning, despite the module updates. Further diagnostic tests on the ACM could be necessary.
- Wiring Harness Issues: Although visually inspected, the wiring harness could have intermittent shorts or opens that occur when exposed to higher temperatures. A more thorough inspection of the harness, including continuity testing at different temperatures, could reveal hidden problems.
- Software or Calibration Issues: While the modules were updated, there’s a possibility that the update itself introduced new problems or that the system requires recalibration. Consulting with Detroit Diesel directly regarding potential software-related issues could be beneficial.
Next Steps
Given the complexity of the issue and the extensive troubleshooting already performed, seeking expert advice from a Detroit Diesel specialist is recommended. They can perform more advanced diagnostics, including:
- ACM Testing: A thorough test of the ACM can determine if it’s functioning correctly.
- Exhaust Gas Temperature Sensor: Verify the accuracy of the exhaust gas temperature sensor, as inaccurate readings can impact NOx efficiency calculations.
- Cylinder Pressure Test: Low compression in one or more cylinders can lead to incomplete combustion and affect NOx emissions.
Addressing this complex issue requires a systematic approach and potentially specialized diagnostic equipment. By consulting with experienced professionals and performing further tests, the root cause of the low NOx conversion efficiency can be identified and resolved.
