Cummins fault code 3261 is a diagnostic trouble code for the Cummins ISX11.9 CM2250 (2010-12) engine that documents the aftertreatment diesel exhaust fluid line heater 2 circuit. This 15-page troubleshooting manual explains what sets the code, the amber warning lamp it activates, and the guided repair steps a technician performs with the Cummins INSITE electronic service tool. It corresponds to SPN 4342 and FMI 5.
Official document details
| Brand | Cummins |
| Model coverage | ISX11.9 CM2250 (2010-12), ISX12 CM2250 (2010-12) |
| System / Group | DTCs – Aftertreatment Diesel Exhaust Fluid Line Heater 2 Circuit |
| Reference codes | SPN 4342, FMI 5, Amber lamp |
| Revision | Last modified 31-Dec-2010 |
| Pages | 15 |
| File size | 0.21 MB |
| Format | |
| Language | English |
Document table of contents
- Overview and circuit description
- Fault code information (SPN 4342, FMI 5, Amber lamp)
- Conditions for running the diagnostics
- Conditions for setting the fault code
- Action taken when the fault code is active
- Conditions for clearing the fault code
- Shop talk and possible causes
- Associated procedures and guided troubleshooting steps
Trucks affected by Cummins fault code 3261
The procedure applies to Cummins ISX11.9 CM2250 (2010-12) engines and the related ISX11.9 CM2250 (2010-12), ISX12 CM2250 (2010-12) platforms fitted to Class 8 on-highway trucks. The steps rely on the Cummins INSITE electronic service tool to read the fault code, monitor the aftertreatment diesel exhaust fluid line heater 2 circuit, and validate the repair. For engine and emissions specifications, consult the Cummins official website.
Who needs this Cummins fault code 3261 manual
Diesel technicians and fleet workshop owners diagnosing DEF line heater 2 circuit fault on ISX11.9 CM2250 engines use this manual to follow the factory-correct sequence instead of guessing at parts. Working from the documented running and setting conditions shortens diagnosis time and helps avoid unnecessary aftertreatment component replacement before the true root cause is confirmed.
Because this document is largely a wiring and connector diagnostic tree, it walks a technician through checking the aftertreatment diesel exhaust fluid line heater 2 circuit circuit, harness continuity, connector pins, and supply voltages before any component is replaced.
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