The manufacturer recommends cleaning the drainage holes every 15,000 km. If you drive the car on country roads, do this more often.
During operation, moisture accumulates in the cavities of the thresholds and doors, causing corrosion. This moisture is removed through drainage holes located at the bottom of the thresholds and doors. Each threshold and each side door have three drainage holes. They are constantly clogged with dirt, i.e. they require cleaning.
Clean the drain holes before washing your car.
Location of drainage holes

1. Clean the drainage holes in the sills with a screwdriver or wire.

2. Clean the drainage holes in the doors in the same way.
