What does it mean wen def comes up on dash board Audi a3?

DEF comes up on the dashboard of an Audi A3 to indicate that the Diesel Exhaust Fluid (DEF) level is low. DEF is a non-toxic, odourless solution that is used in selective catalytic reduction (SCR) systems to reduce emissions of nitrogen oxides from diesel engines.

When the DEF level is low, the engine control unit (ECU) will illuminate the DEF warning light on the dashboard. The driver should then add DEF to the vehicle as soon as possible to avoid any damage to the SCR system.

Here are some things to keep in mind when adding DEF to an Audi A3:

Use only DEF that meets the ISO 22241 standard.

Do not add DEF to the fuel tank.

Do not overfill the DEF tank.

If you spill DEF on the vehicle, rinse it off with water immediately.

DEF is a corrosive substance, so it is important to take precautions when handling it.

If you have any questions about adding DEF to your Audi A3, please consult your owner's manual or a qualified mechanic.