One problem related to door latch has been reported for the 2006 Volvo S40. The most recently reported issues are listed below.
The contact owns a 2006 Volvo S40. The driver side door would not lock intermittently and would making a humming noise in warm weather. The dealer repaired the door so that it locks, but it continues to hum. The front passenger speaker does not work. The dealer has made three attempts to repair the speaker and the humming in the door. The contact is also attempting to implement the lemon law. The current mileage was 28,100 and failure mileage was 6,000. Updated 04-02-08.