P229FNOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Malfunction indicator lamp on
- Often stored together with SCR efficiency code P20EE
- Downstream NOx value implausible compared with the upstream sensor
- Likely causes
- 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)
- RareEngine or dosing software needing an update (several FCA, Hino, Mazda notices)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €1,100
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.