Cummins fault code 4437
J1939 Network #4: erratic or intermittent signal
What it means
Cummins' description: J1939 Network #4 - Data erratic, intermittent or incorrect.
SPN 1668 is J1939 Network #4 - Data erratic. 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
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5, QSF 3.8, QSG 12. 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.
Related ECM, network and data link codes
- 4517 SPN 237 FMI 13
Vehicle Identification Number: out of calibration - 4721 SPN 237 FMI 31
Vehicle Identification Number: condition exists - 4722 SPN 237 FMI 2
Vehicle Identification Number: erratic or intermittent signal - 5133 SPN 2006 FMI 9
Source Address 6: abnormal update rate - 3697 SPN 630 FMI 12
ECM Calibration Memory: bad device or component - 3614 SPN 111 FMI 19
Coolant Level Sensor: network data error
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 4437 mean?
Cummins fault code 4437 is J1939 SPN 1668 FMI 2: J1939 Network #4 - Data erratic, intermittent or incorrect. In plain terms: j1939 network #4: erratic or intermittent signal.
Can I keep driving with Cummins code 4437?
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 4437?
SPN 1668 identifies the part or system (J1939 Network #4 - Data erratic). FMI 2 describes the type of failure: erratic or intermittent signal.
What usually causes Cummins code 4437?
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.