The fuel injectors used on the 5.3L (L59) E85 compatible engine use the USCAR type connector. GM-44602 Fuel Injector Test Adapter (for use with J 39021 Injector Tester) and GM-44603 Fuel Injector Test Lamp are required to properly diagnose the fuel system. These tools are ethanol resistant. GM-44603 was previously essential for Chevrolet, Cadillac, Oldsmobile and Canada and now is needed by GMC and Canadian dealers who didn't received it through a dualled franchise.