Cummins fault code 628
Low #8 LB Cylinder Power: reading below normal (moderately severe)
What it means
Cummins' description: Low #8 LB Cylinder Power.
SPN 1144 is Low #8 LB Cylinder Power. FMI 18 means the value is clearly below normal operating range. It's the middle 'low' level.
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
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 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
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: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 632 SPN 1144 FMI (45)
Low #2 RB Cylinder Power: fault - 648 SPN 1144 FMI 0
High #8 LB Cylinder Exhaust Temperature: reading above normal (most severe) - 652 SPN 1144 FMI (30,45)
High #2 RB Cylinder Exhaust Temperature: fault - 668 SPN 1144 FMI 16
High #8 LB Cylinder Power: reading above normal (moderately severe) - 678 SPN 1144 FMI 4
Cyl #8 LB Exhaust Temp Sens Failed Low: circuit voltage low / shorted low - 712 SPN 1144 FMI (45)
High #2 RB Cylinder Power: fault - 722 SPN 1144 FMI (30,45)
Cyl #2 RB Exhaust Temp Sens Failed Low: fault
Related Battery, power supply and sensor supply codes
- 627 SPN 1143 FMI 18
Low #7 LB Cylinder Power: reading below normal (moderately severe) - 626 SPN 1142 FMI 18
Low #6 LB Cylinder Power: reading below normal (moderately severe) - 625 SPN 1141 FMI 18
Low #5 LB Cylinder Power: reading below normal (moderately severe) - 631 SPN 1143 FMI (45)
Low #1 RB Cylinder Power: fault - 624 SPN 1140 FMI 18
Low #4 LB Cylinder Power: reading below normal (moderately severe) - 623 SPN 1139 FMI 18
Low #3 LB Cylinder Power: reading below normal (moderately severe)
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 628 mean?
Cummins fault code 628 is J1939 SPN 1144 FMI 18: Low #8 LB Cylinder Power. In plain terms: low #8 lb cylinder power: reading below normal (moderately severe).
Can I keep driving with Cummins code 628?
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 628?
SPN 1144 identifies the part or system (Low #8 LB Cylinder Power). FMI 18 describes the type of failure: reading below normal (moderately severe).
What usually causes Cummins code 628?
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.