The Cummins ISX code 3755 manual is a 6-page PDF that documents fault code 3755, the aftertreatment diesel exhaust fluid dosing valve fault reported as data erratic, intermittent or incorrect. It explains that the ECM compares intake and outlet NOx readings to judge SCR conversion efficiency, and that this code is set when a diesel exhaust fluid dosing problem lowers NOx conversion across the SCR catalyst. The procedure is credited to TruckFaultCodes.com and covers the circuit description, component location and full troubleshooting steps.
Official document details
| Brand | Cummins |
| Model coverage | Cummins ISX11.9 CM2250 and ISX12 CM2250 (2010-12) engines |
| System / group | ISX11.9 CM2250 (2010-12) / DTCs |
| Fault code | 3755 (SPN 5394, FMI 2) |
| Warning lamp | None |
| Pages | 6 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code 3755 description
- Circuit description and ECM operation
- Component location
- Shop talk and possible causes
- Step-by-step troubleshooting flow
Applicable truck models
This diagnostic applies to Cummins ISX11.9 CM2250 and ISX12 CM2250 (2010-12) engines. The DEF dosing system components, including the SCR catalyst, DEF dosing unit, controller, dosing valve, tank, lines and NOx sensors, vary in location by vehicle and OEM. The reported cause is a fault in the diesel exhaust fluid dosing system; the diagnostic runs during the INSITE regeneration test. For engine data and authorised service, visit the Cummins official website.
Who needs this Cummins ISX code 3755 manual
Heavy-duty diesel technicians, fleet workshops and owner-operators reach for this manual when fault code 3755 is logged as an information event. It helps an emissions technician trace low SCR conversion to the DEF dosing valve using the guided INSITE test.
Download the ISX code 3755 PDF
The complete procedure, wiring detail and step tables are available in the DiagTechPro manuals library; a free account is required to download the PDF. Keep it alongside the related ISX11.9 CM2250 fault-code sheets listed below.
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