Cummins fault code 2639 is documented on this DiagTechPro library page for Cummins ISM CM871 (2007-09) engines, where it flags a Aftertreatment Diesel Particulate Filter Differential Pressure condition (PID S324, SPN 3251, FMI 0/15). This 3-page PDF reproduces the manufacturer description, shop talk, component location and step-by-step troubleshooting so technicians can confirm and clear the code.
Cummins fault code 2639 overview
Cummins defines this code as “AFTERTREATMENT DIESEL PARTICULATE FILTER DIFFERENTIAL PRESSURE – DATA VALID BUT ABOVE NORMAL OPERATIONAL RANGE – LEAST SEVERE LEVEL” on the Aftertreatment System. The engine aftertreatment system monitors the soot load in the aftertreatment diesel particulate filter. Under normal operating conditions, the aftertreatment diesel particulate filter is self- cleaning, where soot is converted to carbon dioxide, nitrogen, and water. Under light load operating conditions it may be necessary to perform a stationary regeneration of the aftertreatment diesel particulate filter. The soot load in the aftertreatment diesel particulate filter is estimated using the aftertreatment differential pressure sensor and the calculated soot output of the engine. This fault code can be triggered if the application is not operating at duty cycle high enough to regenerate the aftertreatment diesel particulate filter. This fault code indicates that the exhaust temperatures exiting the turbocharger are not high enough to actively regenerate the soot that is trapped in the aftertreatment diesel particulate filter. It may be necessary to increase the duty cycle of the application in order to prevent plugging of the aftertreatment diesel particulate filter.
According to the shop talk notes, possible causes include:
- The engine has been operating in light load operating conditions that prevent exhaust temperatures from being high enough to regenerate the aftertreatment diesel particulate filter.
- A possible engine damage that causes excessive black smoke to be generated. The aftertreatment diesel particulate filter soot loading can be classified into four different stages. As the soot load increases, the AFTERTREATMENT lamp and the Cummins CHECK ENGINE (Amber) or STOP ENGINE (Red) lamp will operate according to the table below. The stationary regeneration procedure can be used to clear the soot from the aftertreatment diesel particulate filter in stages 1, 2, and 3. At level 4, the aftertreatment diesel particulate filter is completely plugged and must be replaced. Inadequate exhaust temperatures entering the aftertreatment system can be a cause of high soot loads in the aftertreatment diesel particulate filter. The duty cycle of the application may need to be increased in order to prevent excessive soot from accumulating in the filter.
Official document details
| Brand | Cummins |
| Model coverage | Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) |
| System / Group | Aftertreatment System — ISM CM871 fault codes |
| Fault code | 2639 (SPN 3251, FMI 0/15) |
| Source | TruckFaultCodes.com Cummins fault code reference (© 2017) |
| Pages | 3 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (PID, SPN, FMI, lamp)
- Description
- Shop Talk
- Component Location
- Troubleshooting Steps
Applicable truck models and engines
This document applies to Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) equipped diesel engines that log Fault Code 2639. Always confirm engine calibration and use a Cummins diagnostic tool such as INSITE to read live data before starting repairs. Full specifications are published on the Cummins official website.
Who needs this Cummins fault code 2639 manual
Heavy-duty truck technicians, fleet workshops and owner-operators diagnosing an electronic control module warning on ISM CM871 engines will use this sheet to verify the fault before parts are replaced.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
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