The present invention relates to a method for localizing a defect in a in-house access plant operable to carry broadband communication services.A method according to the invention further comprises the steps of: instructing a user of said in-house access plant to manipulate in-house equipment through an automated and interactive communication session, determining timing information for each manipulation that is carried out, performing remote quality measurements over said in-house access plant while said in-house equipment are being manipulated, identifying from said timing information a particular manipulation that is time-correlated with a substantial change in measured quality, thereby identifying a particular piece of in-house equipment that has been manipulated and in the neighborhood of which said defect is located. The present invention also relates to an analysis tool such as a network analyzer, a communication unit such an intelligent voice responder or a web server, and to a diagnostic system.