The Complete Cummins Fault Code List (2026)
Cummins engines are renowned for their reliability and durability, but even the best engine can develop faults. Cummins fault codes indicate a malfunction has occurred in one or more of the vehicle’s components. Knowing Cummins fault codes is essential to diagnosing and fixing any problems with your Cummins engine quickly and efficiently. This article will provide an overview of Cummins fault code list reports and offer troubleshooting tips on how to interpret them so you can quickly and easily identify the root cause of any issue quickly and easily.
How to Check Cummins Fault Codes
The best way to check Cummins fault codes is with a diagnostic scanner. We often recommend Jaltest to our clients using Cummins.
Jaltest has expert technicians developing comprehensive, up-to-date coverage of Cummins systems, with 3 software updates per year free of charge.
For shops servicing Cummins engines, Jaltest offers:
Comprehensive Cummins Coverage: Developed by dedicated diagnostic engineers, Jaltest provides extensive coverage across Cummins engine systems, including aftertreatment, fuel systems, emissions, and electronic control modules.
Step-by-Step Troubleshooting: Jaltest provides guided troubleshooting procedures, wiring diagrams, technical data, and repair instructions, going far beyond fault code reading and helping technicians resolve vehicle issues faster.
Live Data & System Monitoring: Jaltest monitors real-time engine parameters, sensor values, and system performance to diagnose intermittent or complex issues early-on.
Bi-Directional Controls & Calibrations: With Jaltest, techs can single-handedly perform forced regens, component activations, injector coding, DPF resets, and other advanced OEM-level service functions with the click of a button.
Predictive Maintenance Capabilities: Predictive maintenance is better than reactive maintenance because it allows you to identify developing issues before they become costly breakdowns. Jaltest’s intuitive platform encourages predictive maintenance best practices to reduce downtime.
Cummins Models Covered by Jaltest in 2026
These are just some of the Cummins CV models covered by Jaltest Diagnostics:
6.7N
B SERIES
B5.9G
BES EV
C8.3G
CELECT
D SERIES
F SERIES
GAS PLUS
ISB
ISC
ISD
ISF
ISG
ISL
ISM
ISV
ISX
ISZ
L SERIES
M SERIES
QSB
R SERIES
X SERIES
Z SERIES
The Complete Cummins Fault Code List (2026 Update)
Here are some of the most common Cummins Fault Codes we see on the job:
Cummins Fault Codes
| Fault Code | Description | Severity |
|---|---|---|
| 212 | Engine Oil Temp Sensor Circuit – Shorted High | Info |
| 259 | Fuel Shutoff Valve Circuit Stuck Open | Info |
| 284 | EPS Sensor #1 (Crankshaft) Supply Voltage – Shorted Low | Info |
| 2962 | EGR Temperature – Above Normal Moderately Severe | Severe |
| 343 | ECM Warning Internal Hardware Failure | Critical |
| 426 | SAE J1939 Datalink – Cannot Transmit | Critical |
| 486 | Injector Metering Rail Pressure Low – Warning | Warning |
| 559 | Injector Metering Rail 1 Pressure | Info |
| 778 | Secondary Engine Speed Sensor Error | Info |
| 1117 | Power Supply Lost with Ignition On | Critical |
| 1922 | Aftertreatment Diesel Particulate Filter Pressure | Severe |
| 2313 | Fueling Actuator #2 Circuit Error | Severe |
| 2372 | Fuel Filter Restriction Moderately High – Warning | Warning |
| 3361 | Intake Manifold 1 Pressure | Info |
| 3382 | Engine Exhaust Gas Recirculation (EGR) System | Severe |
| 3712 | Aftertreatment SCR Operator Inducement | Severe |
| 3725 | Aftertreatment Intake NOx Sensor | Severe |
| 3868 | Aftertreatment Diesel Exhaust Fluid Quality | Severe |
| 4572 | Aftertreatment 1 Diesel Exhaust Fluid Tank Temperature | Severe |
| 4677 | Aftertreatment 1 Diesel Exhaust Fluid Tank Level | Severe |
| 5177 | Variable Geometry Turbocharger Actuator Software | Severe |
| 6254 | Aftertreatment SCR Operator Inducement Severity | Severe |
| 6255 | Engine Protection Derate | Severe |
| 6766 | Aftertreatment 1 Diesel Exhaust Fluid Property | Severe |
Below is a complete list of Cummins fault codes. The first column of the following chart indicates the Suspect Parameter Number (SPN). The second column shows Fault Mode Identifier (FMI) numbers. Followed by a description and then the code itself.
Click on the image above to download the full list!
Understanding SPN vs. FMI vs. OEM Codes in Cummins 2026 Models
With all the acronyms involved, it may get a little confusing. When diagnosing fault codes on newer Cummins engines, especially 2026 emissions-compliant models, it’s important to understand the difference between SPN, FMI, and OEM-specific codes.
What Is an SPN Code
SPN stands for Suspect Parameter Number. It can help you understand what specific system or component is reporting a problem.
SPNs are standardized and consistent across manufacturers.
Example:
SPN 102 = Intake Manifold Pressure
SPN 3216 = Aftertreatment 1 Outlet NOx Sensor
What Is an FMI Code
FMI stands for Failure Mode Identifier and describes how that component (SPN) is failing. It basically answers the question of “what’s wrong?”
FMI codes are paired with SPNs to describe the type of fault detected.
Common FMI examples:
FMI 0 = Data valid but above normal operating range
FMI 1 = Data valid but below normal operating range
FMI 3 = Voltage above normal
FMI 4 = Voltage below normal
FMI 9 = Abnormal update rate
What Are OEM Codes in Cummins?
In addition to SPN/FMI codes, Cummins engines will generate OEM-specific fault codes. These codes are not meant to be easily-accessible unless you have an OEM-level tool like Jaltest.
These are manufacturer-defined codes used internally by Cummins. They provide deeper diagnostic detail than generic J1939 fault descriptions.
For example:
An SPN/FMI may indicate a NOx sensor voltage issue
The Cummins OEM code may clarify whether it’s a heater failure, signal drift, or communication issue
Why This Matters for 2026 Cummins Models
With tighter emissions regulations in 2026 engines, aftertreatment systems (DPF, SCR, NOx sensors) are more sensitive and more complex. You’ll often see:
Multiple SPN/FMI combinations triggered from a single root cause
Derate conditions tied to emissions-related faults
Active + stored codes interacting together
Understanding how SPN, FMI, and OEM codes work together allows technicians to avoid misdiagnosing, prevent downtime, and identify the root cause faster
Check out these videos for additional Cummins training
Best Practices for Maintaining your Cummins Engine in Top Condition
Learn Cummins Fault Codes: To begin with, it's important to become familiar with Cummins fault codes, their meanings, and how to interpret Cummins fault code list reports. As mentioned earlier, Cummins fault codes indicate a malfunction has occurred in one or more of the engine's components. Becoming familiar with Cummins fault codes is essential for diagnosing and fixing any problems quickly and efficiently.
Be Mindful of Wear & Tear: Regularly checking your Cummins engine for signs of wear and tear is also important. Make sure to check fuel injectors, hoses, spark plugs, air filters, oil levels, coolant levels, and other components for any abnormalities.
Review the Cummins Engine’s Service History: it’s essential to keep track of the Cummins engine’s service history and to follow the suggested maintenance schedule outlined by Cummins. Doing so will help you catch and prevent potential problems before they become serious.
In conclusion, Cummins fault codes are essential for diagnosing and fixing any problems quickly and efficiently. It’s important to become familiar with cummings fault codes, their meanings, and how to interpret Cummins fault code list reports in order to identify the root cause of any issue. Additionally, it is important to keep track of your Cummins engine's service history and follow a suggested maintenance schedule outlined by cummings in order to catch potential problems before they become serious issues. By following these best practices for maintaining your cummings engine in top condition, you can ensure that your vehicle runs smoothly at all times!
Looking for more personalized Cummins INSITE & QSOL training? Find out about our Cummins course, where we help expand technicians’ diagnostic skills and capabilities
