When the SCR system fails, the car warns with a countdown of remaining starts: once it passes, the engine will not start again. It pays to act at the first messages, not on the last available start.
Typical symptoms
- "Repair AdBlue system" message or remaining starts on the display (e.g. "starts remaining: 800 km")
- Reduced power
- Engine light and a specific AdBlue light
- Abnormal additive consumption, or none
- Pump noise or hum from the tank
Most common causes
- Urea crystallisation in the injector or line
- Faulty dosing pump or clogged internal filter
- Downstream NOx sensor failure (very frequent cause)
- Level or quality sensor in the AdBlue tank
- Poor-quality or contaminated AdBlue (water, diesel)
- Line heater failure: problems only in freezing weather
What to do
- Do not wait for the last start: after the lock you still need the repair, plus a tow.
- Use additive that meets the standard and do not store it too long.
- Have the errors read: they immediately distinguish NOx sensor, pump and injector.
- Do not overfill or spill AdBlue on the filler neck or plastic parts.
How much it costs
It depends on what failed: a NOx sensor or an injector costs much less than the whole pump. Figures are in how much it costs to repair the AdBlue system.
Disabling the system?
Software disabling of the SCR system is not permitted on the road: it is reserved for off-road, competition or export vehicles.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
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).
AdBlue error: guides by make
Is your problem about a specific make? Read the dedicated guide: Peugeot and Citroën BlueHDi, Opel, Fiat, Mercedes BlueTEC, VAG group. Or the full overview of AdBlue problems by make.
Want an accurate diagnosis? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
What happens when the AdBlue starts run out?
The engine will not restart until the system is repaired and the error cleared in diagnosis.
How much does it cost to repair the AdBlue system?
It depends on the component: a NOx sensor or crystallised injector costs much less than the whole pump. Diagnosis avoids needless replacements.
Can I keep driving with the AdBlue message?
Yes while starts or kilometres remain, but with reduced power; a diagnosis before the count reaches zero is advisable.
Is the fault always the pump?
No: very often it is the NOx sensor or a crystallised injector. Only diagnosis decides which component to replace.
