Knock Sensor (KS)
WARNING: This page is about a different car, the 1996 Saab 9000. However, it is still accessible from the selected car via links, so may be relevant.
See BASIC TESTING article. Since many computer controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in TESTS W/CODES - MOTRONIC 5.2 SYSTEM article.