Cummins fault code 4452
Outlet NOx Sensor Closed Loop Operation: condition exists
What it means
Cummins' description: Aftertreatment 1 Outlet NOx Sensor Closed Loop Operation - Condition Exists.
SPN 520668 is Aftertreatment 1 Outlet NOx Sensor Closed Loop Operation. FMI 31 means the ECM has confirmed the condition described in the code is happening.
NOx sensors sit in the exhaust before and after the SCR catalyst. They measure nitrogen oxides so the ECM can control DEF dosing and confirm emissions are under control. Each sensor has its own small control module and talks over the J1939 network.
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 NOx code shows up once with no lamp, often during cold start or warm-up, and clears.
Schedule a repair
Amber lamp with a NOx sensor code that keeps coming back. It's typically a sensor replacement, and it should be done before it triggers SCR inducement.
Stop and get help
NOx codes alongside a derate or inducement countdown. Get it in now. The truck will keep losing power until the emissions system reads correctly.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Aging NOx sensor reading wrong
- Exhaust leak near the sensor
- Real high NOx from an EGR, DEF or SCR problem
- Sensor contaminated by oil or coolant
What you can check before calling
- Look for exhaust leaks or soot near the sensor locations
- Check the sensor connectors and that the sensor modules are mounted and dry
- Note whether other SCR or DEF codes are active 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: DEF warning lights and derate: what diesel drivers need to know.
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: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Related NOx sensors codes
- 4145 SPN 3255 FMI 9
2 Intake NOx Sensor: abnormal update rate - 3988 SPN 3265 FMI 9
2 Outlet NOx: abnormal update rate - 3749 SPN 3226 FMI 20
Outlet NOx Sensor: data drifted high - 3748 SPN 3216 FMI 20
Intake NOx Sensor: data drifted high - 3725 SPN 3216 FMI 10
Intake NOx Sensor: abnormal rate of change - 3718 SPN 3216 FMI 13
Intake NOx: out of calibration
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 4452 mean?
Cummins fault code 4452 is J1939 SPN 520668 FMI 31: Aftertreatment 1 Outlet NOx Sensor Closed Loop Operation - Condition Exists. In plain terms: outlet nox sensor closed loop operation: condition exists.
Can I keep driving with Cummins code 4452?
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 4452?
SPN 520668 identifies the part or system (Aftertreatment 1 Outlet NOx Sensor Closed Loop Operation). FMI 31 describes the type of failure: condition exists.
What usually causes Cummins code 4452?
The most common causes are: aging NOx sensor reading wrong; exhaust leak near the sensor; real high NOx from an EGR, DEF or SCR problem.
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.