Diesel Exhaust Fluid (AdBlue) Warning Light

What it means

Shown as a fluid container with a drop, sometimes with a short text label, this light is amber and on some makes turns red as the tank nears empty; it means the diesel exhaust fluid (AdBlue) level is low or its treatment system has a fault. On most modern diesels the engine will not restart after it is switched off once the tank runs empty or the fault persists, and the display usually counts down the remaining distance before that happens. A brief glow at key-on that then goes out is normal.

Related lights: Diesel Particulate Filter LightCheck Engine LightGlow Plug Light (Diesel)Water in Fuel Warning Light (Diesel)

Symptoms4

• The light is on with a message showing the distance left before the engine will not restart.
• A message asking you to refill the fluid or reporting an emissions system fault.
• Reduced power or a speed limit on some cars.
• The engine will not restart after being switched off once the fluid runs out.

Possible causes6

• Low diesel exhaust fluid level from normal use (most common).
• Fluid that does not meet the specification or is diluted with water, detected by the quality sensor.
• Faulty fluid pump or dosing injector in the exhaust, or an injector blocked by crystals.
• Faulty tank heater, level sensor or NOx sensor.
• Damaged wiring or connectors in the system.
• Fluid poured into the diesel tank by mistake, a serious error that means the engine must not be started.

How to diagnose5

1. Read the message on the display and note any remaining distance before the no-restart point.
2. Check the fluid level at the blue filler, and look in the owner's manual for its location and tank capacity.
3. If the light stays on after refilling, the car may need a short drive or some time with the ignition on to update the reading.
4. At a workshop: read emissions system codes and test fluid quality, pump pressure, the dosing injector, heater and sensors.
5. If fluid went into the diesel tank, do not start the engine and have the fuel drained right away.

How to fix6

1. Refill with diesel exhaust fluid (AdBlue) that meets the specification, from a trusted source.
2. Drain wrong or contaminated fluid, flush the tank and refill.
3. Clean crystals from the dosing injector or replace it.
4. Replace the pump, heater or level sensor as the tests show.
5. Replace the NOx sensor if it is confirmed faulty.
6. Clear codes and reset the countdown with a scan tool if needed, then confirm the light goes out.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

A refill alone is cheap; the cost rises when the pump, tank heater or NOx sensor must be replaced, which are expensive parts on some cars.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions