Cummins fault code 1256
Control Module Identification Input State Error: erratic or intermittent signal
What it means
Cummins' description: Control Module Identification Input State Error - Data erratic, intermittent or incorrect.
SPN 1563 is Incompatible Monitor/Controller. 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
An amber (yellow) warning lamp means the engine can usually keep running, but the fault should be repaired soon, ideally the same day.
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: QSX 15, 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.
Same SPN, other failure types
Related ECM, network and data link codes
- 1515 SPN 91 FMI 19
SAE J1939 Multiplexed Accelerator Pedal or Lever Sensor System: network data error - 699 SPN 1136 FMI 2
Engine ECU Temperature: erratic or intermittent signal - 698 SPN 1136 FMI 4
Engine ECU Temperature Sensor Circuit: circuit voltage low / shorted low - 697 SPN 1136 FMI 3
Engine ECU Temperature Sensor Circuit: circuit voltage high / shorted high - 427 SPN 639 FMI 9
SAE J1939 Datalink: abnormal update rate - 426 SPN 639 FMI 2
J1939 Network #1: 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 1256 mean?
Cummins fault code 1256 is J1939 SPN 1563 FMI 2: Control Module Identification Input State Error - Data erratic, intermittent or incorrect. In plain terms: control module identification input state error: erratic or intermittent signal.
Can I keep driving with Cummins code 1256?
Usually for a short time, if the engine runs normally and no other warnings are on. Get it diagnosed soon, because many amber codes lead to a derate if ignored. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 1256?
SPN 1563 identifies the part or system (Incompatible Monitor/Controller). FMI 2 describes the type of failure: erratic or intermittent signal.
What usually causes Cummins code 1256?
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.