Cummins fault code 478 is the Cummins ISX11.9 CM2250 diagnostic document for the aftertreatment diesel exhaust fluid controller voltage supply, logged as SPN 444, FMI 16 with a amber lamp. Diesel exhaust fluid injection into the aftertreatment system is disabled while this fault is active. The aftertreatment diesel exhaust fluid controller communicates with the ECM and sets the code when its battery supply voltage is higher than the electrical system voltage. This DiagTechPro library page outlines what the official Cummins troubleshooting procedure contains before you download the full PDF.
Cummins fault code 478 document details
| Brand | Cummins |
| Model coverage | ISX11.9 CM2250 (2010-12), ISX12 CM2250 (2010-12) |
| System / Group | Aftertreatment Diesel Exhaust Fluid Controller Voltage Supply Circuit — DTCs |
| Fault code / SPN / FMI | 478 / SPN 444 / FMI 16 |
| PID / Lamp | P444 / Amber |
| Year / Revision | Not stated in the extract |
| Pages | 10 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Overview and Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- Conditions for Setting the Fault Codes
- Action Taken When the Fault Code Is Active
- Conditions for Clearing the Fault Code
- Shop Talk and troubleshooting steps
Applicable truck models and engines
This Cummins DTC applies to ISX11.9 CM2250 (2010-12) and ISX12 CM2250 (2010-12) engines, and the shared circuit information also references the ISB6.7, ISC8.3, ISL9 and ISX15 CM2250 platforms. Always match the aftertreatment diesel exhaust fluid controller wiring against the OEM diagram before testing, and confirm the diagnosis with the Cummins INSITE electronic service tool. Full engine specifications are published on the official Cummins website.
Who needs this Cummins fault code 478 manual
Workshop technicians, fleet maintenance teams and owner-operators diagnosing a aftertreatment diesel exhaust fluid controller concern on ISX11.9 or ISX12 CM2250 engines use this document to read the CM2250 diagnostic conditions, the action the ECM takes, and the exact steps to clear the code.
The complete PDF (10 pages) is available in the DiagTechPro manuals library; a free account is required to download it. This reference copy helps technicians prepare parts and test steps before servicing the engine.
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