Cummins fault code 426
J1939 Network #1: erratic or intermittent signal
What it means
Cummins' description: J1939 Network #1 - Data erratic, intermittent or incorrect.
SPN 639 is J1939 Network #1, Primary Vehicle Network (previously SAE J1939 Data Link). FMI 2 means the signal is jumping around, dropping in and out, or doesn't make sense compared to other readings.
The engine ECM talks to the transmission, ABS, dash and aftertreatment modules over the J1939 data network. These codes mean the ECM itself, its calibration, or its communication with other modules has a problem.
What the lamp means
This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example.
Keep an eye on it
A network timeout logged once, often during cranking, that cleared.
Schedule a repair
Gauges dropping out, the transmission or ABS acting odd, or codes returning. Book diagnosis. These can go from annoying to stranded quickly.
Stop and get help
Red lamp for an ECM internal failure, or the engine won't start or shuts down. Get it towed or seen where it sits.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- ECM calibration doesn't match the vehicle or another module
- ECM internal failure
What you can check before calling
- Note which other systems acted up: gauges, transmission, ABS
- Check for recent electrical work or aftermarket devices plugged into the diagnostic port
- Check batteries and grounds
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
Related ECM, network and data link codes
- 414 SPN 608 FMI 9
Data Communication error over the J1587 data link Circuit: abnormal update rate - 346 SPN 630 FMI 12
ECM: bad device or component - 343 SPN 629 FMI 12
ECM Warning Internal Hardware Failure: bad device or component - 342 SPN 630 FMI 13
ECM: out of calibration - 341 SPN 630 FMI 2
ECM: erratic or intermittent signal - 319 SPN 251 FMI 2
Real Time Clock: erratic or intermittent signal
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 426 mean?
Cummins fault code 426 is J1939 SPN 639 FMI 2: J1939 Network #1 - Data erratic, intermittent or incorrect. In plain terms: j1939 network #1: erratic or intermittent signal.
Can I keep driving with Cummins code 426?
Usually, yes. This code doesn't normally turn on a lamp by itself, but check for other active codes that might be more serious. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 426?
SPN 639 identifies the part or system (J1939 Network #1, Primary Vehicle Network (previously SAE J1939 Data Link)). FMI 2 describes the type of failure: erratic or intermittent signal.
What usually causes Cummins code 426?
The most common causes are: eCM calibration doesn't match the vehicle or another module; eCM internal failure.
Diesel down in the Midlands?
We work on Cummins-powered pickups, vans and medium-duty trucks across Lexington, Columbia and the Midlands, on site at your yard or roadside.