These instructions apply to the Citroën C4 Mk2 (B71) 2010-2018.
For other models, please choose your vehicle here.
Later diesel (BlueHDi) versions of the Citroën C4 Mk2 (roughly 2014–2018) use AdBlue to clean the exhaust. When the tank gets low you get a warning and a mileage countdown — and at zero the car won’t restart — so top it up before then. It’s an easy owner job.
How to top up AdBlue and clear the warning on a C4 (BlueHDi)
- Find the AdBlue filler with the blue cap (near the diesel filler or under the boot floor).
- Add at least 5 litres of manufacturer-approved AdBlue — never mix it with the diesel tank.
- Switch the ignition on and off 2–3 times without starting, pausing a few seconds each time.
- Start up and drive for 10–20 minutes above about 40 mph (60 km/h) so the system rechecks the level.
- The warning and countdown should clear — occasionally not until the next drive or up to a day later.
If the tank ran completely dry: add at least 5 litres, then wait 5 minutes before touching the car (no doors, key or fob near it) so the refill registers before you restart.
Frequently asked questions
Does my C4 have AdBlue?
Only the later BlueHDi diesels (around 2014 on). Earlier HDi diesels and the petrols don’t use AdBlue.
Why won’t the warning clear after I filled it?
It usually needs an ignition cycle or two and a short drive above 40 mph, and can take until the next day. If it still won’t clear, a level/NOx sensor or pump fault may need a dealer tool.
If the warning persists with a fault light, you can look up the stored code on autodtcs.com.
Independent guide — not affiliated with Citroën. Always follow your official service manual and safety precautions. Read our full disclaimer.