Leaves, rain and blocked water drains — autumn is peak season for water damage to engine control units. What workshops should know now.
When the trees lose their leaves in October and the first heavy rains arrive, peak season for water damage to engine control units begins. Leaves and debris block the water drains under the windscreen — water accumulates in the so-called cowl panel and rises to the level of the control unit. Particularly affected: VW, Audi and BMW, where the engine control unit is often placed directly next to or below this area.
The typical symptoms: the vehicle suddenly won't start; the control unit no longer communicates via OBD; limp mode or rev limiter without apparent cause; traces of moisture or corrosion on the connector and inside the housing.
What workshops can do now: on vehicles that suddenly lose contact with the engine control unit, always check for water ingress first. If water is standing in the footwell or cowl — disconnect the battery, do not attempt further starts. Every additional power surge can permanently destroy the board. Instead, remove the unit and send it to us via our mail-in service.
We clean corroded boards, replace damaged components and seal the board against renewed moisture ingress after repair. The original unit is preserved — including coding and immobiliser. No new part, no recoding.