Cummins fault code 6256
Battery 1 Voltage: reading above normal (least severe)
What it means
Cummins' description: Battery 1 Voltage - Data Valid But Above Normal Operating Range - Least Severe Level.
SPN 168 is Battery Potential / Power Input 1. FMI 15 means the value is somewhat above normal. It's the mildest 'high' level, often an early warning.
The ECM needs clean, steady battery voltage, and it supplies regulated 5-volt power to many sensors. Voltage problems can cause strange codes across many systems at once.
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 low-voltage code after a hard winter start or after the truck sat a while, then clears.
Schedule a repair
Codes return, the truck is slow to crank, or voltage reads low while driving. Test the charging system soon.
Stop and get help
Engine dies, several systems drop out at once, or the ECM loses power. Don't run it until the power supply is fixed. It can leave you stranded.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Weak batteries
- Failing alternator
- Parasitic drain
What you can check before calling
- Check battery terminals and ground straps for corrosion or looseness
- Have the batteries and alternator tested
- Note if several unrelated codes appeared at the same time
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers. For the bigger picture, read our guide: Bad alternator or bad battery? How to tell.
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.
Same SPN, other failure types
- 441 SPN 168 FMI 18
Battery 1 Voltage: reading below normal (moderately severe) - 442 SPN 168 FMI 16
Battery 1 Voltage: reading above normal (moderately severe) - 3724 SPN 168 FMI 17
Battery 1 Voltage: reading below normal (least severe) - 6257 SPN 168 FMI 17
Battery 1 Voltage: reading below normal (least severe)
Related Battery, power supply and sensor supply codes
- 6499 SPN 3597 FMI 17
ECU Power Output Supply Voltage 1: reading below normal (least severe) - 6511 SPN 6655 FMI 3
Maintain ECU Power Lamp: circuit voltage high / shorted high - 6512 SPN 6655 FMI 4
Maintain ECU Power Lamp: circuit voltage low / shorted low - 4954 SPN 3353 FMI 4
Alternator 1 Status: circuit voltage low / shorted low - 4953 SPN 3353 FMI 3
Alternator 1 Status: circuit voltage high / shorted high - 4952 SPN 6655 FMI 4
Maintain ECU Power Lamp: circuit voltage low / shorted low
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 6256 mean?
Cummins fault code 6256 is J1939 SPN 168 FMI 15: Battery 1 Voltage - Data Valid But Above Normal Operating Range - Least Severe Level. In plain terms: battery 1 voltage: reading above normal (least severe).
Can I keep driving with Cummins code 6256?
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 6256?
SPN 168 identifies the part or system (Battery Potential / Power Input 1). FMI 15 describes the type of failure: reading above normal (least severe).
What usually causes Cummins code 6256?
The most common causes are: weak batteries; failing alternator; parasitic drain.
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.