Mobile AdBlue and NOx specialists
Check Anti-Pollution System? What the Warning Means
A common message on Renault and Dacia models and on vans built on Renault platforms. Here is what it means, what you can safely check yourself and when it needs a proper diagnostic.
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7 days a weekSame-day visits where available249 AdBlue faults fixed since May 2026
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Our process
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1
Diagnose
Full diagnostics of the emissions system at your vehicle
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2
Attempt repair
Software repair and re-initialisation of the control modules
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3
Bypass
If necessary, a permanent bypass or deletion with a lifetime warranty
Start with your symptom
What’s happening with your vehicle?
What It Means
What Does “Check Anti-Pollution System” Mean?
The message means the engine computer has logged a fault in a part it treats as emissions-related. On a modern diesel that covers a lot of hardware: the AdBlue (SCR) system, the NOx sensors, the diesel particulate filter, the EGR valve and a range of engine sensors. The same message can also appear on petrol models.
The wording on its own does not tell you which part has failed. Two vehicles showing exactly the same message can have completely different faults, which is why the stored fault code and live data matter far more than the dashboard text.
You are most likely to see this exact wording on:
- Renault and Dacia cars and vans
- Vans built on Renault platforms, such as the Renault Trafic-based Vauxhall Vivaro B and the earlier Renault Master-based Vauxhall Movano, which can show the same or a similar emissions message
- Peugeot, Citroen and DS models, which usually word it as “Antipollution fault” or “Emissions fault: repair needed”
Other makes use different words for the same family of faults. Our AdBlue warning light guide lists the common versions, and our guide to AdBlue system fault messages explains what each one means.
Common Causes
The AdBlue and SCR Faults Behind the Message
When the anti-pollution warning comes from the AdBlue side of the system, these are the faults we find most often. A scan with live data tells us which one it is.
AdBlue Level or Quality
A low tank is the simple one. Fluid that has been diluted, contaminated or left too long can also trigger a warning, because the system checks the quality of what it is spraying, not just how much is left.
Crystallised Injector or Lines
AdBlue dries into hard white crystals. Over time they block the dosing injector and lines, so the system cannot spray the right amount even with a full tank.
Pump and Pressure Faults
A weak or failed AdBlue pump cannot hold the pressure the system expects, which typically logs a pressure code such as P20E8.
NOx Sensor Faults
The NOx sensors check that the system is working. When one drifts or stops reporting, the computer can no longer trust the readings. See our NOx sensor fault page.
Tank Heater or Level Sensor
The tank heater and level sensor sit in the tank assembly. A fault in either can keep the warning on however much fluid is in the tank.
SCR Efficiency Faults
If the catalyst is not reducing NOx as expected, the computer logs an efficiency fault such as P20EE. Our AdBlue fault codes guide explains the common ones.
Not every anti-pollution warning is an AdBlue fault. A blocked particulate filter or a sticking EGR valve can raise the same message, which is why we diagnose before recommending anything. Read more about DPF faults and EGR faults.
Before You Book
What You Can Safely Check Yourself
1. Note everything the dashboard is showing
Once you are parked safely, write down the exact message and any other lights with it: an AdBlue symbol, the engine management light, a mileage countdown or reduced power. A photo of the dash is ideal. That combination tells us far more than the message alone.
2. Check the AdBlue level, and refill only with the right fluid
If the vehicle is also telling you AdBlue is low, refill it with sealed AdBlue marked ISO 22241, through the AdBlue filler, never the diesel filler. Do not use water or any other fluid. Your handbook explains how your vehicle confirms a refill, as some need the ignition on for a short time before the message updates.
3. If it appeared straight after a refill, check the obvious
Make sure the cap is fully closed and that AdBlue went into the AdBlue tank. If AdBlue has gone into the diesel tank, or diesel into the AdBlue tank, do not start the engine and get help first.
4. Do not keep clearing the code
A cheap code reader can switch the light off, but it also wipes the information that points to the cause. If the fault is real it comes back, and you have lost the clues. Our AdBlue warning reset guide explains when clearing a code is worth trying.
5. Know when to stop driving
If the engine management light is flashing, or the engine runs roughly, loses a lot of power, smokes heavily or overheats, stop when it is safe to do so rather than pressing on.
When to Book
When It Needs a Mobile Diagnostic
Book a diagnostic if any of these apply:
- The message is still there after a correct refill, or no refill was needed
- A mileage countdown to a no-start has appeared. Our AdBlue no-start page explains what happens at zero
- The vehicle has gone into reduced power
- The warning keeps coming back after being cleared
- You have been quoted for an expensive part without a confirmed diagnosis
We come to your home, yard or workplace across London, Surrey, Sussex and Kent. At the vehicle we read the stored codes and live data, test the suspect parts and tell you what we have found and what your options are, with a fixed price agreed before any work starts. If the cause turns out to be a DPF or EGR fault rather than AdBlue, we will tell you that too.
Send your registration and the exact message through our quote form and we will come back to you with the next step.
Get a Free Quote & Advice
Peugeot and Citroen
Seeing “Antipollution Fault” Instead?
Peugeot, Citroen and DS use their own wording for the same family of faults, usually “Antipollution fault” or “Emissions fault: repair needed”. The checks above apply in the same way.
Our Peugeot and Citroen pages cover the BlueHDi AdBlue faults we see most, and the Boxer and Relay page covers the vans.
How it works
A clear route to the right solution.
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01
Tell us the symptoms
Give us a few details about your vehicle and the issue.
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02
We diagnose at your location
Our mobile technician comes to you with the right equipment.
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03
You approve the next step
We explain the findings and agree the way forward.
Our pricing
Clear pricing. No surprises.
Diagnostic visit
£185
Fault-code and live-data checks, control module resets and written findings. Included if you go ahead with the full fix on the day.
AdBlue software service
From £249
Diagnostics included. Lifetime warranty on the work. Vehicle and use eligibility checked first.
ECU unlocking, where required, is quoted separately before work starts. What the lifetime warranty covers.
Get a fixed quoteFAQ
Check Anti-Pollution System: Common Questions
It depends on what comes with it. If the vehicle drives normally, with no countdown, no reduced power and no flashing engine light, you usually have time to arrange a diagnostic. If a countdown appears, power drops or the engine light flashes, get it looked at straight away.
Only if low AdBlue was the cause. If the warning stays after a refill with the correct fluid, the system has logged a fault that a refill will not fix.
No. It covers any fault the engine computer treats as emissions-related, including the particulate filter, the EGR valve and engine sensors. A diagnostic with live data is the only reliable way to tell which part is responsible.
Yes. Renault is one of the makes we cover, alongside the Renault-based Vauxhall Vivaro and Movano. Send your registration and the exact message first and we will confirm what we can do for your vehicle.
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