Cummins fault code 726
Cyl #6 RB Exhaust Temp Sens Failed Low: fault
What it means
Cummins' description: Cyl #6 RB Exhaust Temp Sens Failed Low.
SPN 1148 is Cyl #6 RB Exhaust Temp Sens Failed Low. FMI (30,45) means the ECM detected a fault in this system.
Large Cummins engines can have an exhaust temperature sensor at each cylinder's exhaust port. Comparing them lets the ECM spot a cylinder that is running hot, cold, or not firing.
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 single exhaust temperature sensor code with the engine running smoothly.
Schedule a repair
The code keeps returning or several cylinders show imbalance. Book diagnosis. It can hide a real cylinder problem.
Stop and get help
Exhaust temperature imbalance with rough running, smoke or a stop lamp. Shut it down. A cylinder running very hot can burn a piston or valve.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Real imbalance from a weak injector or misfire in that cylinder
- Exhaust leak at the manifold
- Valve problem in that cylinder
What you can check before calling
- Look for heat-damaged wiring along the exhaust manifold
- Note any rough running or smoke
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: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
Related Exhaust temperature sensors codes
- 725 SPN 1147 FMI (30,45)
Cyl #5 RB Exhaust Temp Sens Failed Low: fault - 727 SPN 1151 FMI 4
Cyl #7 RB Exhaust Temp Sens Failed Low: circuit voltage low / shorted low - 724 SPN 1146 FMI (30,45)
Cyl #4 RB Exhaust Temp Sens Failed Low: fault - 728 SPN 1152 FMI 4
Cyl #8 RB Exhaust Temp Sens Failed Low: circuit voltage low / shorted low - 723 SPN 1145 FMI (30,45)
Cyl #3 RB Exhaust Temp Sens Failed Low: fault - 722 SPN 1144 FMI (30,45)
Cyl #2 RB Exhaust Temp Sens Failed Low: fault
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 726 mean?
Cummins fault code 726 is J1939 SPN 1148 FMI (30,45): Cyl #6 RB Exhaust Temp Sens Failed Low. In plain terms: cyl #6 rb exhaust temp sens failed low: fault.
Can I keep driving with Cummins code 726?
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 726?
SPN 1148 identifies the part or system (Cyl #6 RB Exhaust Temp Sens Failed Low). FMI (30,45) describes the type of failure: fault.
What usually causes Cummins code 726?
The most common causes are: real imbalance from a weak injector or misfire in that cylinder; exhaust leak at the manifold; valve problem in that cylinder.
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.