One problem related to side/window air bag has been reported for the 2004 Volvo V40. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Volvo V40 based on all problems reported for the 2004 V40.
The driver's side airbag has failed for no apparent reason. The cost of repair will be around $900. 00 the car was purchased 4 years ago. That is a very costly repair for a relatively young vehicle. I asked the service representative at my authorized Volvo repair shop if I should expect the right side to fail as soon as I repair the left one. He said "no, the right never goes out. " "I had one in just last week- exact same problem as yours. ".