Today, it is almost impossible to repair your engine without knowing the Cummins codes. The problem is, after you get your code numbers, how can you find out what they mean?
Fault codes are Cummins way of letting you know that your engine has a problem. Every sensor and circuit on your engine has a certain expected reading and voltage signal. These signals are monitored constantly by the Cummins ECM. If values rise above or below expected, the ECM will log a code.
If the error has occurred but is not happening at the time of diagnostics, it is known as an Inactive Fault. If the error is happening while you diagnose, it is known as an Active Fault.
All codes can be classified as either Active or Inactive, and their status can be determined by flash codes or through the Insite Electronic Service Tool.
****Update*****
Due to new OBD2 compliance, codes no longer have to be active or inactive. Codes also can be "pending" and also show active even after the problem is repaired. A certain amount of "drive cycles" may be needed to clear a code from the active status. This has also resulted in a major increase in the number of fault codes present in the Cummins ECM. Codes are becoming more "industry standard" in the numbering method, resulting in the original 3-4 digit Cummins codes having new SPN and FMI numbers attached. I'll try to get an updated article on this soon further explaining this change.
If you are tired of browsing the Internet looking for Cummins fault codes, then relax.
Just select your engine to see descriptions of each fault code for your particular Cummins ECM.
ISB Codes - Truck Application (Non - Dodge / Chrysler)
ISB Codes - Dodge Cummins Applications
ISC & ISL Fault Codes- CAPS Fuel System (before 2003)
ISC & ISL Fault Codes- HPCR Fuel System (2003 and later)
ISM Codes - Engines before 2002 (no EGR system)
ISM Codes - Engines After 2002 (with EGR system)
Celect Codes - Includes N14, M11 & L10 engines up to 1995.
Celect Plus Codes - Includes n14, M11 & L10 engines after 1995
ISX Fault Codes - without EGR (Before 2002)
ISX Fault Codes - with EGR (2002 - 2006)
ISX Fault Codes- with DPF (2007-2010)