Referenzöffnung des Tanksystems verstopft

The calibrated orifice used as a reference when testing the evaporative system for leaks, blocked. The system checks for a leak by comparing against a known one — a precisely sized hole — so the reference is what gives the test its scale.

Blocked, the reference reads as no leak at all, which makes every genuine leak look smaller than it is, or makes the test impossible and stores a monitor fault. The component is often part of the leak detection pump assembly. Its position under the vehicle is what blocks it: dust, spray, and insects nesting in a deliberately open passage. Inspect and clear the orifice before condemning the pump, and note that it is calibrated — cleaning must not enlarge it, which would make every leak read smaller.