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P229FModeratePowertrain

P229F: How to Diagnose & Fix — NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)

15 vehicles · 8 makes · $150-$3,500 repair

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How to diagnose and fix P229F: most-reported vehicles

Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.

Mercedes-Benz Sprinter · 2014–2025

Community reported
1,900 owners
Link to this issueError Codes:P207FP20EEP229FP2002

The Sprinter diesel exhaust fluid (DEF/AdBlue) selective catalytic reduction system is plagued by faults in the dosing module, NOx sensors, DEF heater, and SCR catalyst. Failures trigger the dreaded "engine derate" countdown that limits vehicle speed to 5 mph if not resolved, stranding commercial vehicles. The system is sensitive to DEF quality and cold weather.

Common Symptoms

  • Check engine light with SCR fault codes
  • Engine derate countdown warning on dashboard
  • Vehicle limited to 5 mph (derated)
  • DEF warning light illuminated
  • Higher fuel consumption

How to Fix

Diagnose the specific failed component with Star Diagnostics — the system has multiple failure points. Common repairs include the DEF dosing module, NOx sensors, DEF heater element, and DEF quality sensor. Use only ISO 22241-certified DEF fluid. A full SCR reset with Star Diagnostics is required after component replacement.

What you need to fix it

Only diagnosis- and fitment-reviewed repair parts are linked here.

  • PEAK BlueDEF ISO 22241 diesel exhaust fluid, 2.5 gallons
    OEMPEAK DEF002 / ISO 22241-1

    Low-level refill or drain/refill after testing confirms the DEF itself is low, contaminated or out of specification Fitment/availability: The inspected direct U.S.

    The Home Depot

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Owner tips & cautions

  • WarningNever use non-certified DEF fluid. Cheap DEF causes crystallization in the dosing module and destroys the SCR catalyst. Buy from reputable suppliers only. BlueDEF from Peak is widely recommended.
Typical repair cost:$500 - $3,500

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Based on 1,900 owner reports

GoogleRedditYouTubeNHTSA
Community Reported
High Confidence1,900 owner reportsLast reported by owners Mar 2026Reviewed Mar 2026

Ford Transit · 2018–2023

Community reported
60 owners
Link to this issueError Codes:P2201P229FP20EEP207F

EcoBlue diesel Transits have documented owner reports of check engine lights and emissions system warnings related to SCR/DEF operation, commonly tied to NOx sensor faults or SCR efficiency monitoring. When the system detects persistent faults, it may trigger reduced power or countdown-to-no-start strategies depending on market/calibration. These issues are frequently accompanied by emissions-related DTCs and can be intermittent before becoming persistent.

Common Symptoms

  • Check engine light with emissions warnings
  • Reduced power / limp mode
  • DEF/SCR warning messages
  • Increased DEF consumption or abnormal dosing behavior
  • Potential countdown-to-no-start (market dependent)

How to Fix

Diagnose SCR system with a capable scan tool, verify DEF quality, check wiring/connectors at NOx sensors, and replace failed NOx sensor(s) as indicated; perform required resets/adaptations. If applicable per Ford service guidance, update PCM calibration addressing false SCR/NOx diagnostics and confirm proper dosing operation.

Typical repair cost:$350 - $1,800
Sources for this issue (1)
  • NHTSA Manufacturer Communications Data Corpusnhtsa

Research This Issue

Based on 60 owner reports

GoogleRedditYouTubeNHTSA
Community Reported
Medium Confidence60 owner reportsReviewed Apr 2026

Mercedes-Benz GLA · 2015–2023

Link to this issueError Codes:P2002P20E8P229FP0401P0420

GLA diesels (GLA 200d/220d), popular in Germany and the EU, develop clogged EGR valves and diesel particulate filters from soot buildup, plus AdBlue/SCR (NOx reduction) faults. EGR carbon fouling causes rough idle, reduced power and emissions faults; DPF blockage triggers limp mode if regeneration can't complete (common with short urban trips). AdBlue/SCR issues include crystallization from irregular use, sensor/NOx-sensor faults, level/quality warnings and countdown-to-no-start messages. The OM651 also shares timing-chain-stretch tendencies.

Common Symptoms

  • Limp mode / reduced power
  • Check engine and DPF warning lights
  • AdBlue level/quality warning with no-start countdown
  • Rough idle
  • Excessive smoke
  • Increased fuel consumption

How to Fix

Carry out periodic motorway runs to allow active DPF regeneration; clean or replace a clogged EGR valve and clear/replace a blocked DPF. SCR faults require diagnosing and replacing NOx sensors, the SCR/AdBlue metering/dosing unit, or clearing crystallization, then resetting the no-start countdown via XENTRY. Use only fresh, correct-spec AdBlue and keep the tank topped.

Typical repair cost:$300 - $2,500
Sources for this issue (2)
  • Mercedes OM651 & OM654 AdBlue Faults | SCR Fix - Precision Remaps UKarticle
  • Mercedes OM651 diesel engine: common problems, reliabilityarticle

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Community Reported
Medium ConfidenceVerifiedReviewed Jun 2026

Skoda Kodiaq · 2017–2023

Link to this issueError Codes:P2002P20E8P229F

Diesel Kodiaqs used mainly for short urban trips frequently suffer incomplete diesel particulate filter (DPF) regeneration, leading to a clogged filter and recurring warning lights. The associated SCR/AdBlue system (urea pump, injector, NOx sensors) is complex, and a single failed component triggers an emissions fault, sometimes with a no-restart countdown warning. Symptoms include power loss, black smoke, strong exhaust smell and a check-engine light.

Common Symptoms

  • DPF warning light
  • AdBlue/emissions warning with restart countdown
  • Loss of power / limp mode
  • Black smoke on acceleration
  • Strong exhaust smell

How to Fix

Perform a forced/active regeneration and drive at sustained highway speed (around 100 km / ~20-25 min at ~3,000 rpm) to clear the filter; clean or replace the DPF if saturated. AdBlue faults require diagnosing and replacing the specific failed component (NOx sensor, urea injector or pump) and topping up/correcting AdBlue.

Typical repair cost:$250 - $1,500
Sources for this issue (3)
  • Adblue system fault | Skoda Kodiaq SUV Forumforum
  • Skoda Kodiaq 2.0 TDI problems with DPF regeneration | MyCarly Communityforum
  • DPF warning light ON in Skoda Kodiaq. What to check? | DailyDrivenarticle

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026

Chevrolet Silverado 2500HD · 2011–2015

Link to this issueError Codes:P2201P2202P2203P229FP20EE

Early LML trucks (roughly 2011 through 2014) are documented for upstream and downstream NOx sensors that drift out of calibration rather than fail outright. The SCR system compares the two sensors to judge DEF effectiveness; when a sensor reads out of range the truck posts 'DEF Quality Poor' or 'Exhaust Fluid System - See Dealer' and begins a countdown that ultimately limits the truck to a 4 mph creep speed - with perfectly good DEF in the tank. Because the sensors drift in and out of range, the message often comes and goes, which is why owners replace sensors and see the light return. GM has published harness-chafe bulletins covering the same fault codes, so the wiring is a genuine root cause and not just a sensor problem.

Common Symptoms

  • DEF Quality Poor message
  • Exhaust Fluid System - See Dealer warning
  • Speed limiter countdown to 4 mph
  • Check engine light that comes and goes
  • Reduced engine power

How to Fix

Do not replace a NOx sensor on the code alone. Inspect the engine harness for chafing at the routing points covered by GM's chafe bulletins, and check the DEF fluid itself with a refractometer before condemning the sensor. If the sensor is genuinely at fault, replace it with the current-revision part and perform the required sensor relearn/reset with a capable scan tool - skipping the relearn is why many replacements do not clear the message. Emissions components can fall under the federal 8 year / 80,000 mile emissions warranty on these trucks, so check coverage before paying out of pocket.

Typical repair cost:$400 - $1,400
Sources for this issue (3)
  • Check engine...P2201 & P2202 - Chevy and GMC Duramax Diesel Forumforum
  • NOX sensor replaced @ 24k What say you? - Chevy and GMC Duramax Diesel Forumforum
  • NOX sensor question - Chevy Silverado and GMC Sierra Forumforum

Research This Issue

GoogleRedditYouTubeNHTSA
Community Reported
High ConfidenceVerifiedReviewed Aug 2026

Find P229F by make

Browse every documented model and issue for your make.

Chevrolet · 2 issuesDacia · 1 issueFord · 1 issueGenesis · 1 issueMercedes-Benz · 5 issuesOpel · 3 issuesSkoda · 1 issueVolkswagen · 1 issue

P229F code reference

General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.

Frequently asked questions

What does P229F mean?

P229F stands for "NOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)." P229F indicates the engine control module detected a range/performance problem with the downstream NOx sensor on bank 1 (sensor 2), most common on diesel vehicles with SCR/AdBlue emissions systems. The NOx sensor measures nitrogen-oxide levels in the exhaust so the system can dose diesel exhaust fluid correctly and verify the catalyst is working. An implausible or out-of-range signal can trigger emissions warnings, reduced power, and on many diesels eventual no-start countdowns tied to emissions compliance. It is an emissions-system fault that should be addressed before it escalates.

What are the most common causes of P229F?

The most common causes of P229F are: Faulty downstream NOx sensor (bank 1 sensor 2), Wiring or connector corrosion at the NOx sensor, Exhaust leak upstream of the sensor, Contaminated or incorrect diesel exhaust fluid (DEF/AdBlue), SCR catalyst degradation, NOx sensor control-module communication fault, ECM software needing update/recalibration. The specific cause varies by vehicle.

How much does it cost to fix P229F?

Repair costs for P229F range from $150 to $3,500, depending on the vehicle and root cause.

Which vehicles are affected by P229F?

Au7o has documented P229F across 15 vehicle models from 8 manufacturers: Chevrolet, Dacia, Ford, Genesis, Mercedes-Benz, Opel, Skoda, Volkswagen.

Related codes

  • P2290 · Injector Control Pressure Too Low
  • P2293 · Fuel Pressure Regulator 2 Performance
  • P2294 · Fuel Pressure Regulator 2 Control Circuit
  • P229E · NOx Sensor Circuit (Bank 1 Sensor 2)
  • P0020 · Camshaft Position 'A' Actuator Circuit (Bank 2)
  • P0034 · Turbocharger/Supercharger Bypass Valve Control Circuit Low
  • P0035 · Turbocharger/Supercharger Bypass Valve Control Circuit High
  • P003A · Turbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.

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