P229E code meaning
NOx Sensor Circuit (Bank 1 Sensor 2)
Powertrain system Generic code P22xx codes Check engine light
What P229E means
P229E is the basic electrical fault of the second NOx sensor on bank 1, the one behind the SCR catalyst that shows how much NOx survives conversion. Its attached control unit checks the probe lines and passes the result to the engine computer over CAN. GM's 6.6L Duramax (LML) sets the code as Type A when an open or shorted status keeps arriving longer than 10 s, or 0.5 s in a later calibration. Ford's 3.0L and 6.7L diesels use it for shorts and opens on the Vs, COM, Ip1 and Ip2 lines and for a failed internal self-test of the sensor processor; VW's 2014 Touareg TDI for an error message or a validity ratio above 0.5. Volvo and Mack replace the outlet sensor, and Nissan bulletin NTB16-048 does the same on the 2016 Titan XD, adding an ECM update. P2200 is the front sensor.
P229E at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P229E
- Malfunction indicator lamp on
- No valid downstream NOx value in live data
- SCR warning; catalyst efficiency check cannot complete
Common causes of P229E
- Most likelyInternal failure of the outlet NOx probe or its control unit
- PossibleDamaged lead between probe and sensor control unit (heat, chafing)
- PossibleWater or corrosion in the sensor connector
- Less likelyEngine control software needing an update (Nissan Titan XD 2016, NTB16-048)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensorNox sensor wiring
What each part of P229E means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 2 | Area: fuel and air metering (injector circuit). |
| 9E | The exact fault in that area. |
What to do next
- Note P229E and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P229E
What does P229E mean?
P229E means "NOx Sensor Circuit (Bank 1 Sensor 2)". P229E is the basic electrical fault of the second NOx sensor on bank 1, the one behind the SCR catalyst that shows how much NOx survives conversion. It is a generic code, so it means the same on every make.
Is it safe to drive with P229E?
Drive gently and only to a workshop. With P229E the car can go into limp mode (reduced power) to protect itself.
Will P229E fail an emissions test?
Yes, it can. P229E is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P229E to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P229E clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.