If the vehicle diagnostic system determines that the fuel filler cap is loose, improperly installed, or damaged, a "CHECK GASCAP" message will be displayed in the Electronic Vehicle Information Center (EVIC) or Driver Information Display (DID). Refer to "Electronic Vehicle Information (EVIC) or Driver Information Display (DID)" in "Understanding Your Instrument Panel" for further information. Tighten the fuel filler cap until a "clicking" sound is heard. This is an indication that the fuel filler cap is properly tightened. Refer to "Onboard Diagnostic System" in "Maintaining Your Vehicle" for further information.