These instructions apply to the Citroën C3 Mk3 (SX) 2016-2024.
For other models, please choose your vehicle here.
Diesel (BlueHDi) versions of the Citroën C3 Mk3 (2016–2024) use AdBlue to clean the exhaust. When the tank runs low you get a warning and a countdown — and if it reaches zero the car won’t restart — so topping it up in time matters. It’s a simple owner job.
How to top up AdBlue and clear the warning on a C3 (BlueHDi)
- Find the AdBlue filler — usually next to the diesel filler or under the boot floor, with a blue cap.
- Add at least 5 litres of manufacturer-approved AdBlue (don’t put AdBlue in the diesel tank, or diesel in the AdBlue tank).
- Switch the ignition on and off 2–3 times without starting, leaving a few seconds each time.
- Start the car and drive for 10–20 minutes above about 40 mph (60 km/h) so the system re-checks the level.
- The warning and countdown should clear — sometimes 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 keyless fob near it) so the system registers the refill before you restart.
Frequently asked questions
Why won’t my C3 AdBlue warning clear after filling?
It often needs a short drive above 40 mph and an ignition cycle or two, and can take until the next day. If it still won’t clear, a level sensor, pump or NOx-sensor fault may need a dealer tool.
How much AdBlue should I add?
At least 5 litres — a smaller splash often isn’t enough for the system to register a refill and clear the countdown.
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.