Cummins fault code 727
Cyl #7 RB Exhaust Temp Sens Failed Low: circuit voltage low / shorted low
What it means
Cummins' description: Cyl #7 RB Exhaust Temp Sens Failed Low.
SPN 1151 is Cyl #7 RB Exhaust Temp Sens Failed Low. FMI 4 means the voltage on the circuit is lower than possible for a good sensor, usually a short to ground, a damaged harness, or a failed sensor.
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
FMI 4 is an electrical or signal fault, so start with the circuit:
- Exhaust temperature sensor (thermocouple) failed
- Damaged sensor wiring from heat
- Sensor module or connector fault
If the circuit checks out, the reading may be real. Other possibilities: 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
- 726 SPN 1148 FMI (30,45)
Cyl #6 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 - 725 SPN 1147 FMI (30,45)
Cyl #5 RB Exhaust Temp Sens Failed Low: fault - 724 SPN 1146 FMI (30,45)
Cyl #4 RB Exhaust Temp Sens Failed Low: fault - 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 727 mean?
Cummins fault code 727 is J1939 SPN 1151 FMI 4: Cyl #7 RB Exhaust Temp Sens Failed Low. In plain terms: cyl #7 rb exhaust temp sens failed low: circuit voltage low / shorted low.
Can I keep driving with Cummins code 727?
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 727?
SPN 1151 identifies the part or system (Cyl #7 RB Exhaust Temp Sens Failed Low). FMI 4 describes the type of failure: circuit voltage low / shorted low.
What usually causes Cummins code 727?
The most common causes are: exhaust temperature sensor (thermocouple) failed; damaged sensor wiring from heat; sensor module or connector fault.
Diesel down in the Midlands?
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