Your center console, front and rear trunks. If they are not closed all the way until you hear the latch click it causes the beep. Make sure the console is not stuffed with things to the point were it does not latch.
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1987 928S4 Silver Metallic (980)/Navy (TP) 5-Speed
2000 Boxster Speed Yellow/Black 5-Speed
1966 Wife White/Brown Top
1986 Daughter White/Brown Top (Sold!)
1992 Daughter White/Blonde Top