Security Lamp/Indicator: Description and Operation
SKIS INDICATORA Sentry Key Immobilizer System (SKIS) indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional SKIS, this indicator is electronically disabled. The SKIS indicator is located in the upper right corner of the instrument cluster, to the right of the speedometer. The SKIS indicator consists of an icon that represents a key that is circled and crossed-out imprinted on an amber lens. The lens is located behind a cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. The icon appears silhouetted against an amber field through the translucent outer layer of the overlay when it is illuminated from behind by an incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The SKIS indicator lens is serviced as a unit with the instrument cluster lens, hood and mask unit.
The Sentry Key Immobilizer System (SKIS) indicator gives an indication to the vehicle operator of the status of the SKIS. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Sentry Key Immobilizer Module (SKIM) over the Programmable Communications Interface (PCI) data bus. The SKIS indicator bulb is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (RUN/START) circuit. Therefore, the bulb will always be off when the ignition switch is in any position except On or Start. The bulb only illuminates when it is switched to ground by the instrument cluster transistor. The instrument cluster will turn on the SKIS indicator for the following reasons:
- Bulb Test - Each time the ignition switch is turned to the On position, the SKIM tells the cluster to illuminate the SKIS indicator for about three seconds as a bulb test.
- SKIS Lamp-On Message - Each time the cluster receives a SKIS lamp-on message from the SKIM, the SKIS indicator will be illuminated. The indicator can be flashed on and off, or illuminated solid, as dictated by the SKIM message. The indicator remains illuminated until the cluster receives a SKIS lamp-off message from the SKIM or until the ignition switch is turned to the Off position, whichever occurs first.
- Communication Error - If the cluster receives no SKIS lamp-on or lamp-off messages from the SKIM for 20 consecutive seconds, the SKIS indicator is illuminated by the instrument cluster. The indicator remains controlled and illuminated by the cluster until a valid SKIS lamp-on or lamp-off message is received from the SKIM.
- Actuator Test - Each time the cluster is put through the actuator test, the SKIS indicator will be turned on for the duration of the test to confirm the functionality of the bulb and the cluster control circuitry
The SKIM performs a self-test each time the ignition switch is turned to the On position to decide whether the system is in good operating condition and whether a valid key is present in the ignition lock cylinder. The SKIM then sends the proper SKIS lamp-on or lamp-off messages to the instrument cluster. If the SKIS indicator fails to light during the bulb test, replace the bulb with a known good unit. If the instrument cluster flashes the SKIS indicator upon ignition On, or turns on the SKIS indicator solid after the bulb test, it indicates that a SKIS malfunction has occurred or that the SKIS is inoperative. For proper diagnosis of the SKIS, the PCI data bus, or the electronic message inputs to the instrument cluster that control the SKIS indicator, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.