This page covers the Detroit fault code SPN 5018 FMI 18, Diesel Oxidation Catalyst (DOC) Efficiency Fault, on DD Platform engines. It documents the temperature sensor checks and the DPF contamination inspection.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD13, DD15 and DD16 (DD Platform) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Source | TruckFaultCodes.com |
| Year / Revision | 2017 (GHG14) |
| Pages | 5 |
| File size | 0.30 MB |
| Format | |
| Language | English |
SPN 5018 FMI 18 table of contents
- Fault description and 25% derate
- DOC and DPF temperature sensor comparison
- DOC outlet signal wiggle test
- Pressure sensor voltage checks
- DPF contamination inspection
The monitored parameter is exhaust temperature, the monitor is always on, typical duration is 2 seconds, both MIL and CEL illuminate, and the engine reaction is a 25% derate. The code is verified with a parked regeneration.
Diagnosis compares the DOC inlet, DOC outlet and DPF outlet temperature sensors (within 25 degrees C of each other), wiggle-tests the DOC outlet signal, and checks the DOC inlet and DPF outlet pressure sensors (0.44-0.56 volt). The Aftertreatment Device is then removed and the DPF inlet face inspected for coolant, oil or fuel contamination, each pointing to causes such as EGR cooler leaks, turbine seal wear, or fuel dilution. A successful parked regeneration confirms the repair.
Applicable truck models
This guide applies to Detroit DD13, DD15 and DD16 engines under EPA 2007 / GHG14. Sensor removal follows the GHG14 aftertreatment procedures in Power Service Literature, and support runs through the Detroit Customer Support Center. For OEM details, see Detroit’s official website.
Who needs this SPN 5018 FMI 18 manual
Aftertreatment technicians diagnosing a DOC efficiency fault and 25% derate on DD Series trucks use this in-depth guide to check sensors and read the DPF face before replacing the catalyst.
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