P229F — NOx Sensor Circuit (Downstream)
NOx sensor circuit fault (downstream / bank 1 sensor 2).
P229F indicates an electrical or signal fault from the downstream NOx sensor — the one mounted after the SCR catalyst. It is one of the most frequently logged Euro 6 codes on Mercedes Sprinter, BMW, Audi and Land Rover diesels.
P229F symptoms
- AdBlue / Check Engine light
- 'AdBlue — no engine start' countdown
- Intermittent limp mode
- Sister code P20EE often appears alongside
Common causes of P229F
Sensor element failure
Thermal cycling and exhaust contamination degrade the heated zirconia element.
Wiring or connector damage
Heat-damaged loom or corroded connector at the sensor end.
Control module fault (rare)
Some vehicles use a sensor with an integrated module that can fail independently.
Exhaust leak near sensor
Air ingress confuses the signal.
Vehicles affected by P229F
- • Mercedes-Benz Sprinter, Vito, C-Class, E-Class (OM651 / OM642)
- • BMW X5, 5 Series, 3 Series (N57 / B47)
- • Audi A6, A4, Q7 (3.0 TDI)
- • Land Rover Discovery, Range Rover (TDV6 / Ingenium)
- • Ford Transit (2.0 EcoBlue)
- • VW Crafter, Touareg (2.0 / 3.0 TDI)
P229F diagnostic process
- Read live mV / ppm output from upstream and downstream NOx sensors
- Check sensor heater circuit resistance
- Inspect wiring loom and connector
- Confirm fault is sensor-side, not exhaust leak or wiring
Common P229F repairs
- Replace downstream NOx sensor with OE-quality coded part
- Code new sensor to vehicle (Xentry / VCDS / IDS)
- Repair damaged wiring or connector
- Reset SCR adaptations and clear stored codes
Related services
Related coverage areas
Vehicle models commonly logging P229F
Ford Transit AdBlue problems
Van · Ford →
Mercedes Sprinter AdBlue problems
Van · Mercedes-Benz →
Mercedes Vito AdBlue problems
Van · Mercedes-Benz →
Renault Master AdBlue problems
Van · Renault →
Renault Trafic AdBlue problems
Van · Renault →
Peugeot Boxer AdBlue problems
Van · Peugeot →
Peugeot Partner AdBlue problems
Van · Peugeot →
Citroen Relay AdBlue problems
Van · Citroen →
VW Crafter AdBlue problems
Van · Volkswagen →
Vauxhall Movano AdBlue problems
Van · Vauxhall →
Ford Ranger AdBlue problems
Pickup · Ford →
Ford Kuga AdBlue problems
SUV · Ford →
BMW X5 AdBlue problems
SUV · BMW →
BMW 5 Series AdBlue problems
Car · BMW →
BMW 3 Series AdBlue problems
Car · BMW →
Audi Q7 AdBlue problems
SUV · Audi →
Audi A6 AdBlue problems
Car · Audi →
Audi A4 AdBlue problems
Car · Audi →
Mercedes GLE AdBlue problems
SUV · Mercedes-Benz →
Mercedes E-Class AdBlue problems
Car · Mercedes-Benz →
Mercedes C-Class AdBlue problems
Car · Mercedes-Benz →
Range Rover Evoque AdBlue problems
SUV · Land Rover →
Range Rover Sport AdBlue problems
SUV · Land Rover →
Land Rover Discovery AdBlue problems
SUV · Land Rover →
Range Rover Velar AdBlue problems
SUV · Land Rover →
Peugeot 3008 AdBlue problems
SUV · Peugeot →
Peugeot 5008 AdBlue problems
SUV · Peugeot →
Peugeot 308 AdBlue problems
Car · Peugeot →
Peugeot 508 AdBlue problems
Car · Peugeot →
Citroen Berlingo (Passenger) AdBlue problems
MPV · Citroen →
Citroen C4 AdBlue problems
Car · Citroen →
Citroen C5 Aircross AdBlue problems
SUV · Citroen →
VW Tiguan AdBlue problems
SUV · Volkswagen →
VW Passat AdBlue problems
Car · Volkswagen →
VW Touareg AdBlue problems
SUV · Volkswagen →
Related guides
5 / 5
Based on 297+ Google reviews for our sister business Fast Lane Performance — the same team behind Fastlane AdBlue Solutions.
Read all reviews on Google →