Safety Belt Warning Chime
Voltage is supplied to the body control module (BCM) through the following
components when the ignition switch is in the START or RUN position:
When you first turn the ignition switch to the START or RUN position,
a class 2 signal from the BCM is sent to the instrument cluster logic turning
  ON the fasten seat belt indicator. The indicator comes on steady for 20 seconds
  and then flashes for another 55 seconds if the drivers safety belt
  remains unbuckled, or goes out when the drivers safety is buckled. When
the   drivers safety belt is buckled, ground is no longer applied to the BCM
through   CKT 238 (BLK/WHT) from the seat belt switch causing the lamp
and chime   to go out. The chime will only sound for about the first 5 seconds
  of the ignition on cycle.
Key-In Warning Chime
Voltage is supplied at all times to the BCM through the following components:
|     •  | The Underhood Fuse Block TBC fuse | 
 
The chime sounds if all of the following conditions exist:
|     •  | The key is in the ignition switch. | 
 
|     •  | The ignition switch is in one of the following positions: | 
 
|     •  | The LH front door is open. | 
 
When the ignition key is in the ignition switch and the LH front door
is open, the ignition key alarm switch closes. The LH door jamb switch also
  closes. When both of the switches close, the Body Control Module (BCM) senses
  ground through the following components:
|     •  | The LH Door Jamb Switch | 
 
The chime will sound for as long as the door is open and the key is
in the ignition switch.
Lamps-On Warning Chime
Voltage is supplied through the ILLUM Fuse 12 to the BCM through CKT 1220
(GRY) when the following conditions exist:
|     •  | The headlamp switch is in the PARK or Head position | 
 
|     •  | The ignition switch is not in the RUN or START position | 
 
|     •  | The IP dimmer switch is not at the dimmest setting. | 
 
With the IP dimmer switch at the dimmest setting, the current to the
BCM may be too weak to be sensed by the module. When the ignition switch is
  turned to the RUN or START position, voltage is supplied from the GAUGES
 Fuse 4  to the body control module through CKT 39 (PNK).  When
 the ILLUM and  GAUGES Fuse voltages are sensed at the same time, the alarm
 is not sounded.  The GAUGES Fuse 4 loses voltage when the ignition
 switch is in one  of the following positions: