The Audi 80-90 B3 (1986-1991) Diagnostic Tester is a versatile tool that enables users to diagnose and troubleshoot various issues within their vehicle's fuel and ignition systems. It features the ability to read and interpret fault codes stored in the vehicle's control units, allowing users to identify and address problems quickly and efficiently. Additionally, it offers the capability to activate and interrogate the fault memory, providing valuable insights into the vehicle's performance and potential issues.