P229F: NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)
The downstream NOx sensor reading doesn't make sense.
Green, yellow, red: three ways P229F can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Set once.
Schedule a repair
Returns. Replace the sensor soon.
Stop and get help
Countdown or derate. Stop and get help.
Symptoms you might notice
- Check engine light
- DEF or emissions warning
Common causes, cheapest first
- Failing NOx sensor
- Exhaust leak
- Wiring problem
What you can check before calling
- Look for exhaust leaks
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Want the full story? Read our guide: DEF warning lights and derate: what diesel drivers need to know.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
Related codes
More diesel & cummins codes
- P2002
Diesel Particulate Filter Efficiency Below Threshold (Bank 1) - P2463
Diesel Particulate Filter Restriction - Soot Accumulation - P242F
Diesel Particulate Filter Restriction - Ash Accumulation - P2459
Diesel Particulate Filter Regeneration Frequency - P2453
Diesel Particulate Filter Pressure Sensor A Circuit Range/Performance - P2454
Diesel Particulate Filter Pressure Sensor A Circuit 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 P229F mean?
P229F means "NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)". The downstream NOx sensor reading doesn't make sense.
Can I drive with code P229F?
It depends on what the vehicle is doing. Green: Set once. Yellow: Returns. Replace the sensor soon. Red: Countdown or derate. Stop and get help.
What causes P229F?
The most common causes are: failing NOx sensor; exhaust leak; wiring problem.
Is P229F a serious code?
It can be. Countdown or derate. Stop and get help.
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