AdBlue Warning Light On? What to Do

What AdBlue does

AdBlue is a liquid used by many modern diesel cars and vans. It is sprayed into the exhaust, where it breaks down harmful nitrogen oxide gases into harmless nitrogen and water. It has its own tank, usually filled next to the diesel filler or under the bonnet.

A typical car uses a few litres every few thousand miles, so the warning can come as a surprise if you have never had to top up before.

Do not ignore the countdown

When the tank runs low, the dashboard shows a warning, often with a mileage countdown. If the tank runs dry, the car is designed not to start again once you switch it off. It is a legal emissions requirement, not a fault.

Top it up as soon as the warning appears so you are not stuck on the driveway.

How to top up safely

Use AdBlue marked ISO 22241, available at most fuel stations. Fill slowly, avoid spills on paintwork, and some cars need a minimum amount added before the warning will reset.

Never put AdBlue in the diesel tank, or diesel in the AdBlue tank. If it happens, do not start the engine. Call us or a recovery service, as running the engine can damage the fuel or exhaust system.

Warning still on after filling?

If the light stays on after a top-up, or you see a message such as "AdBlue system fault" or "No start in 500 miles", there is a fault in the system. Common causes are a failed level sensor, a heater or pump fault, a blocked injector where AdBlue has crystallised, or a faulty NOx sensor.

These need diagnosing with live data, so the right part is replaced first time.

AdBlue help in Smethwick

ER Automotive tops up AdBlue and diagnoses AdBlue system faults on diesel cars and vans. Call 0121 461 6097 or book online.