The cars we see most often in the workshop with AdBlue problems are Peugeot, Citroën, Opel, Fiat, Mercedes and those of the VAG group. In almost every case the fault is in the NOx sensor, the tank heater, the dosing module or the injector: the message on the dashboard changes, not the method of fixing it, which always starts with diagnosis.
Make by make: what happens
| Make | Typical models | What the dashboard shows | Most frequent faults | Read more |
|---|---|---|---|---|
| Peugeot and Citroën | 308, 3008, 5008, C4, Berlingo, Jumpy | “Antipollution fault” with km remaining | NOx sensor, heater, injector | BlueHDi guide |
| Opel | Insignia, Astra, Zafira, Mokka X, Vivaro | AdBlue fault with km or starts remaining | NOx sensor, pump, injector | Opel guide |
| Fiat | Ducato, Doblò, Talento; Tipo and 500X Euro 6d | SCR fault, often on work vehicles and motorhomes | NOx sensor, injector, heater | Fiat guide |
| Mercedes | C-Class and E-Class, GLC, GLE, Sprinter | “Go to a workshop” message with km remaining | NOx sensors, module, heater | Mercedes guide |
| VAG | Golf, Passat, Tiguan, Audi A3-Q7, Octavia | AdBlue fault with reduced power | NOx sensor, heater, module | VAG guide |
What they have in common
All SCR systems work the same way: a pump brings AdBlue to the injector, which sprays it into the exhaust, and a downstream NOx sensor checks the result. That is why the faults are the same across makes; only the frequency and the cost of the part change. For the full operation see the AdBlue guide.
When to worry
- A countdown in kilometres or starts appears: time is limited.
- The error returns after a top-up: the level is not the problem.
- Power is reduced and the engine light stays on.
- The message appears only in winter: the heater is likely.
How much it costs
In order of cost: NOx sensor or injector €150-400, filter or line €50-200, pump or tank module €600-1,500, SCR catalyst over €2,000. These are indicative figures that change with the model and the type of part; the detail is in how much it costs to repair the AdBlue system. More than the amount, the order matters: diagnosis first, then the part.
What to do, in order
- Read the message and note the remaining kilometres or starts: that is the time you have.
- Do not wait for the countdown to reach zero: once it does, the car will not start.
- Do not top up at random: if the level is low, use only AdBlue that meets ISO 22241.
- Have the SCR system errors and live data read before replacing parts.
- After the repair, ask for the counter reset and, if an NOx sensor was replaced, the adaptation with the diagnostic tool.
What the law says
The SCR system is a type-approved emissions device: on vehicles used on public roads the correct solution is diagnosis and repair, restoring normal operation. Deactivation is not permitted on the road and is reserved for competition, off-road or export vehicles.
How MasterTuning helps
We read the errors with professional tools, check the real SCR parameters (pressure, dosing, NOx sensors, heaters) and replace only the component that has actually failed, with the adaptation procedures when needed. Find the nearest centre or write to us with model, engine, year and the message shown on the dashboard.
Are you a workshop or a technician?
If you diagnose and work on SCR systems, or want to start working on ECUs, the tools are in our shop: Flex (OBD, Bench and Boot) and The Genius (stand-alone, with touchscreen), plus Korhex for protected ECUs. If you already have the equipment, you can get the modified files on mastertuningfile.com (credit price list).
