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Warning lights and alertsUrgency: Garage soon

"Pollution control system faulty" message: causes and the faults that trigger it

"Anticontaminación defectuosa" (emissions system fault) does not point to a specific part: it is a generic warning that the ECU has detected a fault in the system that controls emissions (particulate filter, EGR, catalytic converter, sensors, injection or AdBlue). RACE warns that the wording is not the same on every car, that it is not advisable to drive in this state and that the codes must be read with a diagnostic scanner before replacing anything. If a countdown in kilometres also appears ("engine start not possible in X km"), it points to the AdBlue system, which can end up preventing a restart.[1][2][3]

Colour: yellow or amber. Symbol: a text message on the dashboard ("anticontaminación defectuosa" or similar wording, in English "emissions system fault"), sometimes alongside an amber warning light.

14 documented faults cause it in 11 engines. The most important:

What it means

A common message on Peugeot, Citroën, DS and Opel cars from the Stellantis group. It appears when the ECU detects a fault in a component that controls emissions: the particulate filter, the EGR valve, the sensors, the AdBlue system or, on petrol engines, combustion problems.

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

It is not a specific fault but a generic warning. Have the car diagnosed with the right equipment to read the exact code before replacing any part.

24 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. Saturated particulate filter or regeneration that does not complete

    Common cause

    RACE opens its list of ten causes of this kind of warning with the saturated particulate filter and failed regeneration, and also cites continuous short journeys with a cold engine. When the filter is full, the car protects itself by reducing engine output, with a slight loss of power.[1][4]

    Faults with with the particulate filter

  2. 2. AdBlue/SCR system: level, urea crystals, pump, tank or sensors

    Common cause

    RACE includes AdBlue system problems among the causes, and its guide to the SCR catalytic converter points to three weak points: urea crystallisation on short urban journeys, the NOx sensors and the pump and tank assembly. Autopista warns that once this system's "engine start not possible in X km" countdown has been triggered, improvising usually makes the situation worse.[1][2][3]

    Faults with with AdBlue

  3. 3. Factory-defective AdBlue tank on PSA and Stellantis diesels

    Possible cause

    In 2023 the OCU (Spanish consumer organisation) reported a design flaw in the AdBlue tank of PSA diesels bought from 2015 onwards (explicitly citing the Citroën C3 and C4 and Peugeot diesels) and put the repair at between €800 and €1,200. In 2025 Stellantis opened a compensation platform for Peugeot, Citroën, DS and Opel diesels built between January 2014 and August 2020, and Autofácil names the 208, 308 and 3008 with the 1.6 BlueHDi among the models with defective tanks.[5][6][7][8]

    Faults with with AdBlue

  4. 4. EGR valve blocked by carbon deposits

    Possible cause

    RACE cites it as one of the causes of the anti-pollution warning, and its article on the cost of replacing it explains that carbon build-up can block it until it stops working. Sometimes cleaning it is enough instead of replacing it.[1][9]

    Faults with with the EGR valve

  5. 5. Deteriorated or blocked catalytic converter

    Possible cause

    RACE includes it among the causes of this kind of warning: a catalytic converter that has lost its capacity to convert the gases does not fulfil its emissions control function.[1]

  6. 6. Faulty lambda sensor or differential pressure sensor

    Possible cause

    RACE cites the lambda sensor, which adjusts the air-fuel mixture, and the differential pressure sensor, which monitors the condition of the particulate filter, among the causes of the warning. If they fail, the ECU cannot regulate the mixture properly or monitor the filter.[1]

    Faults with with the engine sensors

  7. 7. Injectors or irregular combustion

    Possible cause

    RACE includes injector faults and irregular combustion among the causes of the warning; among the general symptoms of this type of fault it cites jerking, loss of power, higher consumption, abnormal smoke and a strong smell from the exhaust.[1]

    Faults with with the injectors

  8. 8. Intake or exhaust leaks

    Uncommon

    RACE includes air leaks in the intake or gas leaks in the exhaust among the causes of the warning, without detailing the mechanism.[1]

Depending on what you notice

"Anticontaminación defectuosa" appears on the dashboard

RACE points out that not all cars show the same text and cites variants such as "fallo anticontaminación" or "sistema antipolución defectuoso", and that some cars also show an amber warning light. On a French owners' forum, a Peugeot 3008 1.6 BlueHDi lit the engine warning light and, just afterwards, showed an equivalent message ("antipollution défaillante") with a countdown in kilometres.[1][10]

Emissions fault and AdBlue on a Peugeot 3008

Autofácil includes the 3008, along with the 208 and 308, among the cars with the most common AdBlue faults on the 1.6 BlueHDi engine, mainly due to defective tanks or filling difficulties. On the French forum, one user says that after the warning with a countdown, the diagnosis was an AdBlue pump starting to seize, fixed by replacing the tank; it is an isolated case, so confirm it with a diagnostic scan.[8][10]

Emissions system fault on a Peugeot 308

The sources consulted do not discuss the message on the 308 specifically, but Autofácil lists it among the Peugeot 1.6 BlueHDi models with defective AdBlue tanks, and the OCU reported in 2023 a defect in that tank on Peugeot diesels bought after 2015. First of all, check the AdBlue level and ask for a diagnostic scan to find out whether the origin is that system or another, such as the particulate filter or the EGR.[1][6][8]

Emissions system fault on a Citroën C4

The OCU named the Citroën C3 and C4 among the diesels with a factory defect in the AdBlue tank (bought from 2015, with a repair of €800 to €1,200), and Stellantis covers part of those repairs on Citroën diesels built between January 2014 and August 2020. If your C4 is petrol or from another period, the warning may come from any of the other causes, so the first step is to read the codes.[5][6][7]

The warning comes with a countdown such as "engine start not possible in X km"

That countdown belongs to the AdBlue system: Autopista warns that once it is triggered, improvising usually makes the situation worse, and a user on the French forum points out that this countdown message is specific to that system. First check whether the AdBlue tank is empty; if it is not, a diagnostic scan is needed before it reaches zero, because with a genuine SCR fault the car may go into limp mode or refuse to restart.[2][3][10]

What to check first

  1. Pay attention to how the car is running: loss of power, jerking, abnormal smoke, a strong smell from the exhaust or protection mode. If any of these symptoms is present, do not keep driving.[1]
  2. If the warning comes with a countdown in kilometres, check the AdBlue level and top up with approved product if it is low.[2][3]
  3. If the level is correct or the warning does not go away, ask a garage for a code read-out with a diagnostic scanner and have them identify the affected part before replacing anything.[1]
  4. Do not clear the fault without repairing it: RACE warns that this only hides the problem temporarily. After repairing, clear the code and check that the warning does not return.[1]
  5. If your diesel is a Peugeot, Citroën, DS or Opel from between 2014 and 2020 and the origin is the AdBlue tank, keep the invoices and check Stellantis's compensation platform before paying for the repair.[5][7]
  6. Bear it in mind if the ITV (Spain's roadworthiness inspection) is approaching: RACE notes that an anti-pollution system fault can count against it, because it includes emissions checks and an OBD read-out.[1]

Can I keep driving?

Urgency: Garage soon

It should not be left. RACE considers that it is not advisable to drive with this warning, because prolonged use increases pressure and temperature and can damage other parts. If the warning comes with an AdBlue countdown, the car keeps running while kilometres remain, but Autopista warns that carrying on with a genuine SCR fault can lead to limp mode, prevent restarting or aggravate a fault that was initially minor; go to the garage before it reaches zero. If there is also loss of power, jerking or smoke, stop.[1][3]

How much it costs to fix

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

RepairPrice
Replacing the EGR valve (part and labour, according to RACE)[9]€130 – €800
Replacing the defective AdBlue tank on a PSA diesel (OCU figure from 2023, depending on the garage)[5][6]€800 – €1,200
Replacing the particulate filter on a mid-value car (RACE; labour is extra)[4]€800 – €1,000
Reconditioning the particulate filter at a garage that opens and empties it (RACE, "around" this figure)[4]€400

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 2.0 HDi[11]

  2. Source for the symptom in the 2.2 HDi[12]

  3. Source for the symptom in the 1.6 HDi[13]

  4. Source for the symptom in the 2.0 BlueHDi[11]

  5. Source for the symptom in the 1.6 HDi[14]

  6. Source for the symptom in the 2.0 TDI[15]

  7. Source for the symptom in the 1.5 dCi[16]

  8. Source for the symptom in the 1.6 / 2.2 i-DTEC[17]

  9. Source for the symptom in the 1.3, 1.5 and 1.6 gasolina (serie M)[18]

  10. Source for the symptom in the 1.5 dCi[19][20]

  11. Source for the symptom in the 1.3 TCe[21]

  12. Source for the symptom in the 2.2 i-CTDi[22]

  13. Source for the symptom in the M270/M274[23]

  14. Source for the symptom in the 1.3, 1.5 and 1.6 gasolina (serie M)[24]

Which cars it appears in

These faults affect 11 engines. We have documented 120 models from 20 makes with some of the affected versions: open yours to see all its faults.

Engines

Cars with the affected versions

Pollution control faulty: causes in your car

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

Audi 4
Citroën 18
Dacia 5
DS 4
Fiat 1
Ford 6
Honda 8
Mazda 1
Mercedes-Benz 8
MINI 1
Nissan 5
Opel 2
Peugeot 19
Renault 15
Seat 4
Škoda 3
Suzuki 4
Toyota 1
Volkswagen 7
Volvo 4

Pollution control faulty 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

What does the "anticontaminación defectuosa" message mean?

It is a generic warning: the ECU has detected a fault in the emissions control system, which can include the particulate filter, the EGR, the catalytic converter, the sensors, the injectors or AdBlue. RACE points out that the wording varies from car to car and that the cause can only be known by reading the codes with a diagnostic scanner.[1]

Can I keep driving with the emissions warning?

RACE does not recommend it, because driving like this increases pressure and temperature and can damage other components. If what you have is an AdBlue countdown, the car works while kilometres remain, but Autopista warns that carrying on with a genuine fault can lead to limp mode or prevent restarting.[1][3]

Does topping up AdBlue clear it?

Only if the car detected nothing but the lack of fluid and no other code is stored: then topping up properly and driving a little, or doing a start cycle, can normalise the system. If the SCR has recorded a genuine fault, a diagnostic scan is needed.[3]

Can I pass the ITV with this warning?

RACE warns that an anti-pollution system fault can count against you in the ITV (Spain's roadworthiness inspection), because the inspection includes emissions checks and a read-out of the OBD system.[1]

Is it a known defect on Peugeot, Citroën, DS and Opel?

What is documented is a defect in the AdBlue tank of PSA diesels: the OCU reported it in 2023 and, according to El Español, Stellantis opened a compensation platform in 2025 for Peugeot, Citroën, DS and Opel diesels built between January 2014 and August 2020. It is not the only possible cause of the message.[5][6][7]

How much does it cost to fix?

Since it is a generic warning, it depends on the part. As a reference, RACE puts replacing an EGR valve at between €130 and €800, the OCU put replacing the PSA AdBlue tank at between €800 and €1,200, and RACE gives €800 to €1,000 plus labour for a new particulate filter.[4][5][9]

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.¿Te falla el sistema antipolución de tu coche?RACE · Motoring press · published 25 September 2026 · consulted 4 October 2026 · in Spanish
  2. 2.Qué es un catalizador SCR: funcionamiento, AdBlue y mantenimientoRACE · Motoring press · published 23 September 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.¿Qué es el filtro de partículas y para qué sirve?RACE · Motoring press · published 26 January 2021 · consulted 4 October 2026 · in Spanish
  5. 5.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
  6. 6.La OCU denuncia a Citroën y Peugeot: no han notificado el defecto de estos modelosVozpópuli · General press · published 26 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 precio tiene cambiar una válvula EGR?RACE · Motoring press · published 17 June 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.Fiabilité du 2.0 HDIFiches-Auto · Motoring press · consulted 27 September 2026 · in French
  12. 12.Essai, avis et fiabilité des 2,2 HDI 136 chevauxFiches-Auto · Motoring press · consulted 27 September 2026 · in French
  13. 13.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
  14. 14.¿Qué es el aditivo del filtro de partículas de mi diésel?Diariomotor · Motoring press · consulted 26 September 2026 · in Spanish
  15. 15.Maxi-fiche fiabilité - Audi A4 (2007-2015) : belle, mais capricieuseCaradisiac · Motoring press · published 1 April 2023 · consulted 26 September 2026 · in French
  16. 16.Vanne EGR : problèmes et pannesFiches-auto.fr · Motoring press · published 24 January 2023 · consulted 26 September 2026 · in French
  17. 17.Fiabilité et pannes Honda CR-V (2012-2019)Fiches-auto.fr · Other source · consulted 27 September 2026 · in French
  18. 18.Fiabilité et pannes Suzuki Swift (2005-2010)Fiches-auto.fr · Owners' forum · consulted 8 October 2026 · in French
  19. 19.Fiabilité du Dacia Duster 2 : la maxi-fiche occasion de CaradisiacCaradisiac · Motoring press · published 27 April 2022 · consulted 26 September 2026 · in French
  20. 20.Maxi-fiche fiabilité - Renault Clio 5 : loin d'être irréprochableCaradisiac · Motoring press · published 19 April 2024 · consulted 26 September 2026 · in French
  21. 21.Renault-Dacia. Quel bilan fiabilité pour le moteur 1.3 TCe ?L'argus · Motoring press · published 5 April 2021 · consulted 27 September 2026 · in French
  22. 22.Fiabilité et pannes Honda CR-V (2007-2013)Fiches-auto.fr · Other source · consulted 27 September 2026 · in French
  23. 23.Mercedes M274: Typische Probleme & HaltbarkeitGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
  24. 24.Rückruf Suzuki SX4AUTO BILD · Motoring press · published 7 April 2008 · consulted 8 October 2026 · in German