The Vehicle Theft Security System (VTSS) is divided into two basic subsystems: Vehicle Theft Alarm (VTA) and Sentry Key Immobilizer System (SKIS). Following are the recommended procedures for diagnosis of each of these two subsystems.To avoid serious or fatal injury on vehicles equipped with airbags, disable the supplemental restraint system before attempting any steering wheel, steering column, airbag, occupant classification system, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the proper precautions could result in accidental airbag deployment.The hard wired circuits between components related to the VTA system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.However, conventional diagnostic methods will not prove conclusive in the diagnosis of the VTA system or the electronic controls or communication between other modules and devices that provide some features of the VTA system. The most reliable, efficient, and accurate means to diagnose the VTA system or the electronic controls and communication related to VTA system operation requires the use of a diagnostic scan tool. See the Vehicle Theft Security System menu item on the scan tool. Refer to the appropriate diagnostic information.To avoid serious or fatal injury, on vehicles equipped with airbags, disable the supplemental restraint system before attempting any steering wheel, steering column, airbag, occupant classification system, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the proper precautions could result in accidental airbag deployment.The hard wired circuits between components related to the SKIS may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SKIS or the electronic controls or communication between other modules and devices that provide some features of the SKIS. The most reliable, efficient, and accurate means to diagnose the SKIS or the electronic controls and communication related to SKIS operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.SENTRY KEY IMMOBILIZER SYSTEM DIAGNOSISCONDITIONPOSSIBLE CAUSESCORRECTIONSECURITY INDICATOR FAILS TO LIGHT DURING BULB TEST1. Ineffective Light-Emitting Diode (LED).1. Use a diagnostic scan tool to perform the instrument cluster actuator test. Refer to the appropriate diagnostic information.2. Ineffective fuse.2. Check the SKREEM/WCM fused B(+) fuse and the fused ignition switch output (run-start) fuse in the Totally Integrated Power Module (TIPM). Replace the fuses, if required.3. Ineffective ground circuit.3. Test and repair the open ground circuit at the connector for the SKREEM, if required.4. Ineffective battery feed circuit.4. Test and repair the open battery feed circuit at the connector for the SKREEM, if required.5. Ineffective ignition feed circuit.5. Test and repair the open ignition feed circuit at the connector for the SKREEM, if required.SECURITY INDICATOR FLASHES FOLLOWING BULB TEST1. Invalid key in ignition switch lock cylinder.1. Replace the key with a known valid key.2. Key-related fault.2. Use a diagnostic scan tool and the appropriate diagnostic information for further diagnosis.SECURITY INDICATOR LIGHTS SOLID FOLLOWING BULB TEST1. SKIS system malfunction/fault detected.1. Use a diagnostic scan tool and the appropriate diagnostic information for further diagnosis.2. SKIS system ineffective.2. Use a diagnostic scan tool and the appropriate diagnostic information for further diagnosis.