P229F code meaning
NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)
Powertrain system Generic code P22xx codes Check engine light
What P229F means
P229F says the rear NOx sensor on bank 1 is electrically sound but its reading fails a plausibility test. Methods vary. GM's 6.6L LML waits for a burst of engine-out NOx and faults the sensor if its own value moves by less than 3 ppm (Type B); the 3.0L LZ0 watches the stability of the internal pump currents, failing above 0.5 percent unstable time. Ford checks offsets of roughly 30 ppm low or 50 ppm high and a missing rise on tip-in; VW's 2014 Touareg TDI checks offset, self-diagnosis results and oxygen plausibility. Volvo and Mack explain that P229F-64 can set when a fresh SCR leaves almost no NOx, so a single event is no proof of a bad sensor. Hino wants DEF quality and dosing checked first, and Ford warns that EGR cleaning fluids poison NOx sensors.
P229F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P229F
- Malfunction indicator lamp on
- Often stored together with SCR efficiency code P20EE
- Downstream NOx value implausible compared with the upstream sensor
Common causes of P229F
- Most likelyOutlet NOx element drifted, slow or poisoned (e.g. sodium from cleaning fluids)
- PossiblePoor DEF quality or faulty dosing that distorts downstream NOx
- PossibleHarness or connector fault at the outlet sensor (Volvo/Mack P229F-64)
- Less likelyEngine or dosing software needing an update (several FCA, Hino, Mazda notices)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensorSCR catalyst
What each part of P229F 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). |
| 9F | The exact fault in that area. |
What to do next
- Note P229F 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 P229F
What does P229F mean?
P229F means "NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)". P229F says the rear NOx sensor on bank 1 is electrically sound but its reading fails a plausibility test. It is a generic code, so it means the same on every make.
Is it safe to drive with P229F?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P229F fail an emissions test?
Yes, it can. P229F 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 P229F to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P229F clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.