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Warning lights and alertsUrgency: Garage soon

AdBlue system warning: causes and the faults that trigger it

The AdBlue warning appears when the control unit detects that fluid is running low or that something is wrong with the SCR system on modern diesels. Normally the first warning arrives with about 2,000 to 2,500 km in hand, in yellow or orange, and then becomes more insistent with a countdown in kilometres; if the tank runs empty or the fault is not corrected, the car may refuse to start once you switch it off. If the level is correct and the warning does not go away after topping up, you need a diagnosis at a garage before the countdown reaches zero.[1][2][3]

Colour: yellow or amber. Symbol: AdBlue system warning in the instrument cluster, yellow or orange at first, usually accompanied by a text message and, later on, a countdown in kilometres.

16 documented faults cause it in 16 engines. The most important:

What it means

Diesels with selective catalytic reduction (SCR) use AdBlue to cut NOx emissions. A warning with a countdown ("engine will not restart in X km") indicates a low level or a fault in the AdBlue tank, pump, heater or injector. When the countdown reaches zero, the car will not start again.

General explanation from MotorFiable. How it shows up in each engine, with sources, is in the list of faults.

What to do now

Garage soon

If the tank is full and the warning persists, the problem lies with the system. Go to a garage before the countdown ends and keep your receipts in case the fault is covered by a manufacturer campaign.

27 sourcesHow we work

Most common causes

From most to least likely according to the sources. Under each cause, the part and the related OBD codes.

  1. 1. Low AdBlue level

    Common cause

    This is the most common reason for the first warning. Autopista puts the first warning at about 2,000 to 2,500 km of AdBlue range, and Motorpasión explains that a steady orange light usually indicates a low level, with a margin of between 1,700 and 2,400 km depending on make and model. If the car had only detected the lack of fluid and has no other fault stored, topping up with approved product usually returns the system to normal.[2][3][4]

    Faults with with AdBlue

  2. 2. Urea crystals in the injector, the lines or the tank

    Common cause

    On short city journeys the exhaust does not get hot enough and deposits of crystallised urea can form that affect the injector, the lines or another component of the system, according to RACE. Motorpasión includes blocked injectors and crystallised deposits among the faults that trigger the warning even when the level is correct, and Autopista lists them among the reasons the warning does not go off after topping up.[1][2][4]

    Faults with with AdBlue

  3. 3. Faulty pump, heater or tank

    Possible cause

    RACE explains that when the electrical part of the tank assembly fails (the built-in pump or the heater that prevents freezing), the usual fix is to replace the whole tank. Motorpasión puts figures on these repairs: the heater is around 800 euros, and the pump or the complete tank can exceed 1,500 and 1,800 euros.[1][4]

    Faults with with AdBlue

  4. 4. Faulty level or NOx sensors

    Possible cause

    NOx sensors measure the gases before and after the catalytic converter and, according to RACE, can degrade with extreme heat. Motorpasión and Autopista also cite faulty sensors among the reasons the warning appears or does not go away even though there is fluid in the tank.[1][3][4]

    Faults with with the engine sensorsFaults with with AdBlue

  5. 5. Dosing fault due to low pressure in the system

    Possible cause

    A Jaguar Land Rover technical bulletin for several Land Rover and Range Rover models associates code P20E8 (reductant pressure too low) with the engine fault light and with a dosing fault message accompanied by a countdown until the engine will no longer start. It asks you to first check for leaks, damage or loose connectors on the tank, the supply line and the dosing module.[5]

    Faults with with AdBlueP20E8

  6. 6. Factory-defective AdBlue tank on Peugeot, Citroën, DS and Opel diesels

    Possible cause

    In 2023 the OCU (Spanish consumer organisation) denounced a design flaw in the AdBlue tank of PSA diesels bought from 2015 onwards, with a warning light that keeps appearing asking for the car to be repaired, and put the cost of replacing the tank at 800 to 1,200 euros. In January 2025 Stellantis opened a compensation platform for Peugeot, Citroën, DS and Opel diesels built between January 2014 and August 2020, and Autofácil cites the 208, 308 and 3008 with the 1.6 BlueHDi engine among the models with defective tanks or filling problems.[6][7][8]

    Faults with with AdBlue

Depending on what you notice

How to reset the AdBlue warning light

If the car only detected a lack of AdBlue and there is no other code stored, topping up with approved product and driving for a while, or doing a start cycle, may normalise the system; Repsol says that simply starting the engine is enough for it to recognise the new level. If the SCR has registered a real fault, the control unit stores the code and you will normally need a diagnosis at a garage. Autopista also warns that tampering with the emissions control alters the type approval and can end in an MOT failure (in Spain, the ITV inspection).[3][9]

The AdBlue warning light doesn't go off after topping up

Try the basics first: wait a few minutes, switch the ignition on several times and check the manual; depending on the car you may need to add between 5 and 10 litres, and Motorpasión warns that with less than 4 or 5 litres the sensor may not register the change. If the tank is well filled and the warning stays on, Autopista points to a sensor, urea crystals or an SCR system fault and recommends going to a garage with diagnostic equipment. On PSA diesels with the defective tank, the OCU describes a warning light that keeps coming back.[2][3][4][6]

The dashboard says "engine start impossible in X km"

This is the countdown with which the car warns you of the point after which it will not let you start it again. When it is down to a low level, it comes after a yellow or orange warning that becomes more insistent (Repsol puts the second alert at around 1,000 km); but it can also appear because of a dosing fault with fluid in the tank, as in the Jaguar Land Rover bulletin or in the case of a 2018 Peugeot 3008 1.6 BlueHDi described by a user on a French forum ("will not start in 1,100 km"). Autopista advises against improvising once the countdown is active.[2][3][5][9][10]

AdBlue fault on a Peugeot 3008 (and AdBlue warning light on other Peugeots)

Autofácil includes the 3008, along with the 208 and 308 with the 1.6 BlueHDi engine, among the cars with the most common AdBlue faults, mainly because of defective tanks or filling difficulties. There is a tank defect denounced by the OCU on PSA diesels and a Stellantis compensation scheme for Peugeot, Citroën, DS and Opel diesels from 2014 to 2020. On a French forum, about a 3008 with the same kind of warning, a user says the diagnosis was an AdBlue pump starting to seize and that it was resolved by replacing the tank; this is an isolated case, so confirm it with a diagnosis.[6][7][8][10]

AdBlue warning light on a Peugeot Partner

The sources consulted do not cover the Partner separately, so the general guidelines apply: check the level, top up with approved AdBlue and, if the warning persists, ask for a diagnosis. What they do document is a tank defect on Peugeot diesels built between January 2014 and August 2020, with a Stellantis compensation programme based on age and mileage; if your Partner falls within that period, keep your invoices and check the platform before paying.[2][6][7]

What the AdBlue warning light symbol looks like and what colour it is

The sources describe the warning by its colour and message rather than by the drawing: it starts in yellow or orange, steady, with a text indicating a low level, and becomes more insistent until it shows, on some cars, a countdown in kilometres. If you see that warning, the AdBlue tank is usually low.[2][4]

What to check first

  1. Note the message that appears and, if there is a countdown, the kilometres it shows: the warning starts in yellow or orange and becomes more insistent as they drop.[2][3]
  2. Check that AdBlue really is low and top up with approved product (ISO 22241 standard). Never put it in the fuel tank.[1][3]
  3. After topping up, wait a few minutes, switch the ignition on several times or start the engine and drive for a while. If the level was very low, add enough: with less than 4 or 5 litres the sensor may not register the change.[2][3][4][9]
  4. If the warning stays on, or there is a countdown with the tank full, ask for a diagnosis with code reading before it reaches zero. Do not tamper with or disable the system.[3][5]
  5. If your diesel is a Peugeot, Citroën, DS or Opel from between 2014 and 2020 and the fault is in the tank, keep your invoices and check the Stellantis compensation platform before paying for the repair.[6][7]
  6. If you mostly do short city journeys, alternate with runs on the open road at a steady pace so the exhaust heats up: very short trips encourage urea crystals.[1]

Can I keep driving?

Urgency: Garage soon

It depends on the stage of the warning. With the first warning there is some margin (the sources talk about 2,000 to 2,500 km, and Repsol puts the second alert at around 1,000 km), so topping up in time solves it. If there is already a countdown with the tank full, it is a fault: take it to a garage before it reaches zero. With an empty tank the car does not stop while running, but once switched off it may refuse to start until you top up, and Repsol adds that power drops drastically; so do not leave it too late and do not switch off the engine far from somewhere you can top up.[1][2][3][9]

How much it costs to fix

Indicative prices published by the sources cited; they depend on the car and the garage.

RepairPrice
Topping up AdBlue with a 5 to 10 litre container (product only, at around 0.90 euros per litre on average at the pump, in Spain)[2]€8 – €25
Replacing the defective AdBlue tank on a PSA diesel (OCU figure from 2023 in Spain, depending on the garage)[6]€800 – €1,200
Replacing the tank heater (Motorpasión puts it "around" this figure, in Spain)[4]€800
Replacing the AdBlue pump (Motorpasión says it can exceed this figure, in Spain)[4]€1,500
Replacing the complete tank with its built-in components (Motorpasión says it can exceed this figure, in Spain)[4]€1,800

Documented faults that cause it

Specific engine and gearbox faults, from most to least important (severity × frequency). Below each title, how the symptom shows up in that fault.

  1. Source for the symptom in the 1.5 BlueHDi[11]

  2. Source for the symptom in the 1.6 HDi[12][13][14]

  3. Source for the symptom in the 2.0 HDi[6]

  4. Source for the symptom in the OM642[15]

  5. Source for the symptom in the 2.0 BlueHDi[14]

  6. Source for the symptom in the 2.0 Ingenium diésel[16]

  7. Source for the symptom in the OM654[17][18]

  8. Source for the symptom in the D4/D5[19]

  9. Source for the symptom in the 1.5 dCi[20]

  10. Source for the symptom in the BMW B57[21]

  11. Source for the symptom in the 2.3 MultiJet[22]

  12. Source for the symptom in the OM656[23]

  13. Source for the symptom in the 1.6 CDTI[24]

  14. Source for the symptom in the 1.5 / 2.0 EcoBlue[25]

  15. Source for the symptom in the 2.2 MultiJet / BlueHDi (Stellantis)[26]

  16. Source for the symptom in the 2.3 dCi (M9T)[27]

Which cars it appears in

These faults affect 16 engines. We have documented 130 models from 16 makes with some of the affected versions: open yours to see all its faults.

Engines

Cars with the affected versions

AdBlue warning: causes in your car

130 cars have several documented faults that cause this symptom. Choose yours to see only those that affect it, by engine and by year.

BMW 5
Chrysler 1
Citroën 13
Dacia 5
DS 5
Ford 13
Iveco 1
Jaguar 3
Jeep 1
Mercedes-Benz 26
Nissan 4
Opel 13
Peugeot 16
Renault 10
Toyota 3
Volvo 11

AdBlue warning by brand

Fault codes that may go with it

If you have an OBD reader, the code stored by the control unit helps you work out which system is failing.

Frequently asked questions

How many kilometres can I drive with the AdBlue warning light on?

It depends on the model. Autopista talks about 2,000 to 2,500 km at the first warning, Motorpasión about 1,700 to 2,400 and Repsol about 2,000, with a second alert from 1,000 km. If the warning comes from a fault and not from the level, the figure on the countdown shown on your dashboard takes precedence.[2][4][5][9]

What happens if AdBlue runs out?

According to Autopista, the engine does not stop while running for safety reasons, but when you switch off the ignition the control unit may prevent a new start until you fill the tank. Repsol adds that the car goes into a safety mode with a drastic reduction in power. RACE recommends never letting the level run too low.[1][2][9]

Can the AdBlue warning light be reset without a diagnostic machine?

Only if the car detected nothing but the lack of fluid and no other code is stored: then filling the tank properly and driving for a while, or doing a start cycle, may be enough. If the SCR system has registered a real fault, the control unit stores the code and a diagnosis is normally needed.[3]

How much does it cost to top up AdBlue and how often do you need to?

Autopista puts the pump price at about 0.90 euros per litre on average in Spain (June 2026) and 5 and 10 litre containers at 8 to 15 and 15 to 25 euros. Repsol calculates consumption at roughly one litre every 1,000 km and Motorpasión says a tank can last between 10,000 and 20,000 km depending on driving style.[2][4][9]

What happens if I disable AdBlue to get rid of the warning?

Autopista warns that tampering with or disabling the emissions control alters a basic condition of type approval and can cause problems at the MOT (in Spain, the ITV inspection) and at a roadside check. The solution it recommends is to identify the affected component and repair it.[3]

Can I claim if my Peugeot, Citroën, DS or Opel diesel fails because of the AdBlue tank?

In 2025 Stellantis opened a compensation platform for diesels of those brands built between January 2014 and August 2020. According to El Español, it covers 100% of parts up to 5 years and 150,000 km, between 30 and 90% from 5 to 8 years depending on mileage, and labour at 30 euros per case. Confirm the current terms on the official platform before counting on it.[6][7]

Other symptoms: warning lights and alerts

All symptoms

Has this happened to you? Tell us which fault it was, at how many kilometres and how much you paid: it helps other owners know what to expect. Report your fault.

Sources

Every fact on this page links to its source. If you find an error, let us know.

  1. 1.Qué es un catalizador SCR: funcionamiento, AdBlue y mantenimientoRACE · Motoring press · published 23 September 2026 · consulted 4 October 2026 · in Spanish
  2. 2.Aviso de AdBlue encendido, qué hacer y cómo rellenarloAutopista · Motoring press · published 26 June 2026 · consulted 4 October 2026 · in Spanish
  3. 3.¿Se puede resetear el fallo AdBlue sin máquina de diagnosis? Riesgos y alternativasAutopista · Motoring press · published 16 April 2026 · consulted 4 October 2026 · in Spanish
  4. 4.El pequeño aviso que algunos conductores de diésel se saltan porque «aún quedan 2.000 km»: ignorarlo puede ser un carísimo errorMotorpasión · Motoring press · published 12 March 2026 · consulted 4 October 2026 · in Spanish
  5. 5.SSM72610 - DTC P20E8 - Reductant pressure too low - signal above allowable rangeJaguar Land Rover · Manufacturer · published 29 January 2016 · consulted 4 October 2026
  6. 6.El fallo que afecta a cientos de coches y que ahora la OCU denuncia para reclamar indemnizacionesAutopista · Motoring press · published 29 May 2023 · consulted 4 October 2026 · in Spanish
  7. 7.Stellantis crea una plataforma para los afectados por los motores Puretech y depósitos AdBlue: ¿qué debo hacer?El Español · General press · published 21 January 2025 · consulted 4 October 2026 · in Spanish
  8. 8.Los coches más afectados por las averías de AdBlue en el mercado actualAutofácil · Motoring press · published 22 June 2026 · consulted 4 October 2026 · in Spanish
  9. 9.¿Qué es el AdBlue? Todo lo que necesitas saberRepsol · Other source · published 14 November 2024 · consulted 4 October 2026 · in Spanish
  10. 10.antipollution defaillant ne ne demarre plus dans 1100kmL'argus (foro de propietarios) · Owners' forum · published 1 June 2022 · consulted 4 October 2026 · in French
  11. 11.Solución fallo AdBlue Peugeot, Citroën y Opel: evita cambiar el depósitoST Automoción · Other source · published 11 December 2025 · consulted 26 September 2026 · in Spanish
  12. 12.PSA 1.5-1.6-2.0 BlueHDi. Défaut du réservoir d'Adblue pris en chargeL'argus · Motoring press · published 6 March 2021 · consulted 26 September 2026 · in French
  13. 13.Stellantis ataca el problema del AdBlue con una medida especial para los afectados de Peugeot y CitroënMotor.es · Motoring press · published 13 December 2024 · consulted 26 September 2026 · in Spanish
  14. 14.Adblue : problèmes en pagaille ?Fiches-Auto.fr · Motoring press · consulted 26 September 2026 · in French
  15. 15.Abgas-Skandal: KBA findet angeblich deutliche Hinweise auf illegale Abschalteinrichtungen in Mercedes-Dieselautosheise online · General press · published 14 July 2017 · consulted 26 September 2026 · in German
  16. 16.Fiabilité Jaguar XE, pannes et témoignagesFiches-auto.fr · Owners' forum · consulted 27 September 2026 · in French
  17. 17.Fiabilité Mercedes Classe E (2016-2023)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  18. 18.Fiabilité Mercedes GLC (2015-2022)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  19. 19.Fiabilité et pannes Volvo V60Fiches-auto.fr · Other source · consulted 27 September 2026 · in French
  20. 20.Fiabilité du Dacia Duster 2 : la maxi-fiche occasion de CaradisiacCaradisiac · Motoring press · published 27 April 2022 · consulted 26 September 2026 · in French
  21. 21.Motor BMW B57: fiabilidad y averíasDasercars · Motoring press · consulted 4 October 2026 · in Spanish
  22. 22.Fiat Ducato 2.3 MultiJet: AdBlue, SCR y modo de emergencia (diagnóstico)KFZ Dietrich (taller, Alemania) · Other source · published 10 September 2026 · consulted 8 October 2026 · in German
  23. 23.Mercedes AdBlue-Systemstörung | s. Betriebsanleitung | Symptome, Ursachen, Kosten & LösungswegeCarWiki · Technical documentation · consulted 9 October 2026 · in German
  24. 24.Twin dosing en diésel: el fallo que dispara una avería de más de 1.000 euros en el tallerMotor16 · Motoring press · published 22 September 2026 · consulted 27 September 2026 · in Spanish
  25. 25.Fiabilité Ford : pannes par modèle et générationFiches-auto.fr · Other source · consulted 27 September 2026 · in French
  26. 26.DVSA – base de llamadas a revisiónDVSA (Reino Unido) · Official body · consulted 9 October 2026
  27. 27.Fiabilité Renault Master 2.3 dCiCarverif · Other source · consulted 5 October 2026 · in French