Leaves, rain and clogged drainage channels — 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 clog the drainage channels beneath the windscreen — water accumulates in the so-called cowl area and rises to the control unit's mounting location. Particularly affected: VW, Audi and BMW, where the engine control unit is often positioned directly next to or beneath this area.
Typical symptoms:
- Vehicle suddenly fails to start
- The control unit no longer communicates via OBD
- Limp mode or rev limit without apparent cause
- Traces of moisture or corrosion on the connector and inside the housing
What workshops can do now:
For vehicles that suddenly lose communication with the engine control unit, always check for water ingress first. If water is standing in the footwell or cowl area — disconnect the battery, do not attempt further starts. Every additional power surge can permanently destroy the circuit board. Instead, remove the unit and send it to us via our mail-in service.
We clean corroded circuit 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.