P229F91 Mercedes Fault Code: Causes & How to Fix
If you own a Mercedes-Benz with an AdBlue SCR system, encountering the P229F91 Mercedes fault code is not uncommon. This Diagnostic Trouble Code (DTC) indicates an issue with the NOx sensor circuit on Bank 2, leading to increased emissions and reduced engine efficiency.
In this guide, we’ll explain:
- What the P229F91 fault code means
- Why it happens
- Step-by-step solutions to fix it
What Is the P229F91 Mercedes Fault Code?
The P229F91 error occurs when the NOx sensor in Bank 2 fails to measure nitrogen oxide levels correctly. This sensor is crucial for emissions control, and a malfunction can trigger various performance issues, such as:
- Check engine light illuminated
- Increased fuel consumption
- Thick black smoke from the exhaust
- Reduced engine power
Mercedes Models Affected
This issue commonly affects:
- Sprinter W906
- W222, W205, W212, S212, A207, C207
- W213, W238, GLC, W166 GLE Bluetec
What Causes the P229F91 Fault Code?
Several factors can trigger the P229F91 Mercedes error:
- Faulty NOx Sensor (Bank 2) – The sensor may be damaged or malfunctioning.
- Wiring Issues – Short circuits, open wires, or poor connections.
- AdBlue Contamination – Poor-quality AdBlue can disrupt sensor performance.
- Exhaust Buildup – Excessive soot deposits affecting NOx sensor readings.
The P229F91 code may also appear with related errors:
- P2202, P2200, P2201, P220162, P2203 (NOx sensor circuit malfunctions)
- P2204, P220400, P220000 (Sensor performance issues)
How to Fix P229F91 Mercedes Fault Code – 6 Essential Steps
If you need support for error code P229F91 or AdBlue, please contact VCCarTool technician at WhatsApp: +1 (901) 414 – 1927 for the fastest error resolution support!
1. Scan for Fault Codes Using Xentry
To properly diagnose the issue:
- Connect Xentry to the OBD2 port
- Perform a full vehicle scan
- Check for additional NOx-related errors
2. Inspect the NOx Sensor and Wiring
A damaged sensor or faulty wiring can trigger P229F91. Check for:
- Loose or corroded connections
- Broken wires or damaged insulation
- Secure sensor mounting
If wiring issues exist, repair or replace them before moving forward.
3. Verify AdBlue Quality & Exhaust System
Poor AdBlue quality or a contaminated exhaust can contribute to P229F91. Follow these steps:
- Ensure the AdBlue cap is sealed
- Check and refill AdBlue levels
- Drain and clean the AdBlue tank if needed
- Perform exhaust regeneration to clear soot buildup
4. Reset & Reprogram the NOx Sensor
If the NOx sensor is intact but the error persists:
- Use Xentry to reset the NOx sensor
- Run the NOx sensor adaptation process
- Clear all fault codes and test drive the vehicle
5. Inspect the Wiring Using Electrical Schematics
If the issue continues, check the vehicle wiring diagram for deeper troubleshooting:
- Use Alldata, Autodata, or Starfinder to locate circuits
- Find potential shorts or broken connectors
- Replace faulty components if needed
6. Replace the NOx Sensor (If Necessary)
If all else fails, the NOx sensor module may need replacement:
- Install a genuine Mercedes-Benz NOx sensor
- Calibrate the new sensor using Xentry
Need Professional Help? Contact VCCARTOOL!
If you’re struggling to fix P229F91 Mercedes fault code, let our expert technicians assist you remotely.
- WhatsApp: +1 (901) 414 – 1927
- Email: [email protected]
Conclusion
The P229F91 Mercedes fault code can cause severe engine inefficiencies if left unresolved. Following this step-by-step guide, you can:
- Diagnose the error with Xentry
- Inspect and repair wiring & connections
- Check AdBlue quality & perform exhaust maintenance
- Reset, reprogram, or replace the NOx sensor
For fast, reliable NOx sensor troubleshooting, VCCarTool is here to help. Contact us today!