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AdBlue Guide

AdBlue and NOx sensor faults

AdBlue Delete and Removal enquiries should start with identifying the actual fault. AdBlue warnings and NOx sensor codes can have several causes, and a dashboard message alone does not prove that a sensor needs replacing. Send your registration, postcode and warning details so we can check the likely SCR specification and discuss mobile assessment.

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01Understanding the service

AdBlue and NOx Sensor Faults Explained

SCR uses AdBlue dosing to help reduce nitrogen oxides in the exhaust. NOx sensors measure nitrogen oxide levels; depending on the system, sensors before and after the SCR catalyst support dosing control and efficiency monitoring. A warning may result from a sensor fault, wiring damage, communication loss, incorrect dosing or poor SCR performance. Some faults can trigger a restart-inhibition countdown, but the warning sequence varies by vehicle. These generic code descriptions are starting points, not component diagnoses; manufacturer-specific subcodes also matter.

  • P20EE: SCR NOx catalyst efficiency below threshold, bank 1.
  • P208E: Reductant injection valve stuck closed, bank 1 unit 1; this does not by itself prove a blockage.
  • P229F: NOx sensor circuit range/performance, bank 1 sensor 2.
  • U029E: Lost communication with NOx sensor B.
  • P207F: Reductant quality performance; this does not by itself prove contaminated AdBlue.

Diagnostic Checks and Vehicle Fitment

SCR is fitted to many UK diesel cars and vans, including relevant Mercedes-Benz BlueTEC, Citroën and Peugeot BlueHDi, and Land Rover Ingenium diesel variants. Fitment and sensor layout depend on the exact model, engine, build date and emissions specification; the badge or engine family alone is not enough. SCR-equipped vehicles are not confined to the 2015 to 2023 period. Send your registration so we can check the likely specification, with diagnostic confirmation where needed.

  • Read all relevant control modules and record fault subcodes and freeze-frame data before clearing anything.
  • Check sensor power supplies, earths, wiring, connectors and communication where indicated.
  • Assess NOx readings under suitable operating conditions rather than condemning a sensor from one code.
  • Check dosing pressure, injector operation, exhaust leaks and exhaust temperatures as the fault requires.
  • Check fluid condition and applicable manufacturer software guidance where relevant.

Repair and Software Changes Are Different

A repair should address a demonstrated cause rather than rely on trial-and-error replacement. Manufacturer software updates or guided resets may form part of a repair where applicable, but they are not the same as disabling SCR monitoring. A bypass does not restore dosing, sensor accuracy or catalyst performance. After repair, appropriate functional tests and any required adaptations should confirm whether the system is working correctly.

    Mobile Assessment and Restart Warnings

    Send your current postcode and describe where the vehicle is parked so we can confirm coverage, access and whether mobile assessment is suitable. Include whether it starts and the exact wording of any countdown. Some faults need workshop facilities or further testing, so roadside completion and avoidance of recovery cannot be promised. If the vehicle displays a restart restriction, follow its handbook guidance and seek an assessment promptly.

      Information to Send Before Assessment

      A few details help distinguish a fluid-level warning from a dosing, sensor or communication fault. Please provide whatever information you have; do not replace parts solely on the basis of a generic code description.

      • Vehicle registration and mileage.
      • Current postcode and parking or access details.
      • A clear photo of the complete dashboard message.
      • Fault codes, including manufacturer-specific subcodes if available.
      • Recent AdBlue top-ups, repairs or software work.
      • Whether the warning is intermittent, a countdown is active or the engine will not restart.
      How it works

      What Happens When We Visit?

      From booking to completion, our experienced mobile technicians make the process straightforward.

      1. 1

        Book Your Appointment

        We confirm your vehicle, location, service and appointment.

      2. 2

        Technician Calls With ETA

        On the day, your technician calls with an estimated arrival time.

      3. 3

        We Arrive & Diagnose

        We connect diagnostic equipment, check the vehicle and identify relevant faults.

      4. 4

        ECU Software Work

        We read the original ECU software, prepare the AdBlue modification and apply it.

      5. 5

        Final Checks & Resets

        Final diagnostics, applicable fault-code resets and checks to confirm the agreed work is complete.

      6. 6

        Payment & Receipt

        We take payment, provide a receipt and explain the applicable software warranty.

      02Why choose Fix My AdBlue

      • Operating Since 2012
      • Experienced Technicians
      • 5.0★ Genuine Google Reviews290+ Verified Google Reviews
      • Nationwide Mobile Service Across England
      • No Fix, No FeeSubject to terms
      • Lifetime Software WarrantyCovers the software we install
      • 24/7 Emergency Callouts AvailableAdditional emergency callout charge applies

      Customer questions

      Questions customers ask us

      Still unsure? Send us your registration and a photo of the warning on WhatsApp.

      Ask on WhatsApp
      What is AdBlue Delete?

      AdBlue Delete generally refers to software changes intended to disable SCR dosing and associated monitoring. It does not repair a failed NOx sensor, pump, injector or wiring fault. The effects depend on the vehicle and software, so it should not be described as a guaranteed cure for warning lights or restart restrictions. Send your registration and fault details for an assessment.

      What is AdBlue Removal?

      AdBlue Removal is often used to describe a software bypass rather than physical removal of the tank or other SCR components. It is not a repair, and the term alone does not establish what changes are proposed or whether other engine faults will remain.

      What is the difference between AdBlue Delete and AdBlue Repair?

      AdBlue Repair aims to restore correct SCR operation by diagnosing and addressing the underlying fault. Depending on the findings, that may involve wiring repairs, a suitable software update, dosing-system work or replacement of a confirmed faulty component. Disabling monitoring is different from restoring the system, and a properly diagnosed repair is not inherently temporary.

      What is an AdBlue Fix?

      AdBlue Fix is a general description, not a specific procedure. The appropriate work depends on the fault codes, live readings and physical checks. Clearing codes alone does not establish that the fault has been resolved, and a restart countdown may require vehicle-specific checks and procedures.

      What vehicle and postcode information do you need for a quote?

      Please send your registration, mileage, current postcode, dashboard message and any diagnostic codes. Your registration helps identify the likely vehicle specification, but a VIN check or diagnostic scan may be needed to confirm SCR fitment, installed components and ECU software. Your postcode helps us check mobile coverage and access.

      Can I send my warning light photo on WhatsApp?

      Yes. Send a clear photo of the complete warning message, including any remaining-distance countdown, together with your registration. Photos help with initial assessment but cannot confirm whether a NOx sensor, dosing component or electrical fault is responsible.

      Do you offer 24/7 emergency callouts?

      Yes. Our standard hours are Monday to Sunday, 8 AM to 8 PM. Emergency callouts are available 24 hours a day, 7 days a week, subject to location and availability. An additional emergency callout charge applies and is confirmed before dispatch.

      Related

      290+ Verified Google Reviews

      Featured 5-Star Customer Reviews

      Real reviews from real Fix My AdBlue customers, taken straight from Google.

      5.0 on Google

      290+ Verified Google Reviews

      • “Friendly and efficient service, sorted out my adblue issue and did a stage 1 remap on my range rover. Would use again”

        Dec Halford

        3 Oct 2026

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      • “Happy with the remap done on my car to fix the adblue fault. The engineer was polite and efficient. I would highly recommend the company.”

        Michael Carrington

        2 Oct 2026

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        1 Oct 2026

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      • “Excellent job, arrived exactly when he said he would. Cured my adblue problem with ease ,also remaped”

        norman cass

        1 Oct 2026

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      • “Thank you so much for sorting my adblue fault And remap much appreciated for the quick response And did the job outside my door No travelling to get to you You came to me And The pleasant Technician who did the job thanks so much very happy Customer”

        john Vaughan

        1 Oct 2026

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      • “Really happy with the remap done on my car, polite, efficient service and would highly recommended to anyone. Fixed my Adblue problem and cleared all my lights on the dashboard. My car is now quicker and more fuel efficient, I’m more than happy and very grateful for the service I received.”

        Sean Phillips

        30 Sept 2026

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      • “Excellent service from start to finish. I had an AdBlue fault with my vehicle and they diagnosed and fixed the problem quickly and professionally. Very knowledgeable, efficient and friendly service, and they kept me informed throughout the process. The vehicle is now running perfectly again. I’m really impressed with the service and would highly recommend AdBlue Service to anyone having AdBlue or related vehicle problems. Great job and thank you! 👏🚗”

        Mauricio Carturan

        27 Sept 2026

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      • “Very quick and efficient as well as cost friendly. Good availability as well, Had an adblue fault so couldn't drive, came to my house and solved the issue as well as remapping the car. Thumbs up for quick communication.”

        Ramiz Abdullah

        25 Sept 2026

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      • “Spent a few hundred pounds on diagnostics for other garages to say it cannot be fixed quickly or cheaply but then I found Adblue Fix and they came out to me the following morning and sorted the issues within 20 minutes. I highly recommend them and the life time warranty was a great addition.”

        Sam B

        11 Sept 2026

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      • “Quick, on time, honest about pros and cons of adblue remap, and professional. And, of course, they came to me. Can't really ask for more than that”

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        2 Sept 2026

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      • “This company fixed my ad blue system fault and remapped my car too. Very quick and efficient service totally recommend from a very happy customer thanks guys”

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        31 Aug 2026

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        27 Aug 2026

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        27 Aug 2026

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      • “I would highly recommend E.G. to anyone with issues with the adblue system in there vehicle they were absolutely brilliant and the technician went above and beyond to solve my issue, they get 10 out 10 from me”

        Johnny brown

        25 Aug 2026

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      • “Very satisfied with work on my Citroen berlingo Adblue fix would highly recommend to anyone very polite thank you”

        Sean Cummins

        21 Aug 2026

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      • “Lost count of the amount of Adblue issues I’ve had on my van. Another company had tried previously to fix it but weren’t able to. Tried again with these guys and it was sorted the same day I called! Highly recommended!”

        Robert Lamond

        20 Aug 2026

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      • “Very happy with my adblue removal recommendation is very high from me to people and a hassle free service”

        Adam Rawlings

        19 Aug 2026

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      • “Fixed the adblue fault on my van. The light come on a Friday and unfortunately my van had MOT on the monday. These guys come out on Sunday and fixed my adblue issue so I was still able to get to my MOT on the Monday. Really great service, the guy that come out was polite and efficient. Can't fault these guys at all, I highly recommend.”

        Sam Geddes

        19 Aug 2026

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      • “I was having issues with the Adblue system and was quoted a lot of money elsewhere to get it. I found these who did it for a fraction of the price and they did a great job. 5* all day long”

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        26 Jul 2026

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      1 / 20
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