If a vehicle runs out of AdBlue, the vehicle’s exhaust system will not be able to reduce nitrogen oxides (NOx) emissions as effectively. Depending on the vehicle and the regulations it is subject to, the vehicle may enter a “limp mode” or “reduced power mode” where the engine’s power is limited to protect it from damage. The vehicle may also display a warning message or indicator on the dashboard. It’s important to refill the AdBlue tank as soon as possible to ensure the vehicle can continue to operate normally and meet emissions regulations.