My door locks, fuel flap and near all vacuum components are in need of attention. During my troubleshooting I discovered that there is an electrical vacuum pump in the trunk, I thought all vacuum was supplied by the engine pump. Can someone explain to me what is the function of this pump and under what parameter it operates. It is very difficult to troubleshoot something you don't know how it's suppose to operate. For example: are all locks vacuum operated (I don't see any lines going into the front doors).