Voltage is supplied to the truck 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 START or RUN, voltage from the truck BCM is supplied to the fasten seat belt indicator through CKT 237 (YEL). The indicator remains lit for about 5 seconds.

If the driver safety belt is not buckled, a ground is applied to the truck BCM through CKT 238 (BLK/WHT) from the seat belt switch. The chime or buzzer will sound for about 5 seconds.

Voltage is supplied at all times to the truck BCM through the following components:

The chime or buzzer sounds if the following conditions exist:

When the door is open, the LF door jamb switch closes to ground. This provides a ground to the truck BCM through the following components:

The chime or the buzzer will sound for as long as the door is open and the key is in the ignition switch.

Voltage is supplied through the ILLUM Fuse 3 to the BCM through CKT 41 (BRN) when the following conditions exist:

With the panel dimmer switch at the dimmest setting, the current to the truck BCM may be too weak to be sensed by the module. When the ignition switch is turned to RUN or START, voltage is supplied through GAUGES Fuse 4 to the alarm module through CKT 39 (PNK). The two voltages are sensed. The alarm is not sounded.

GAUGES Fuse 4 loses voltage when the ignition switch is in one of the following positions:

The BCM senses the change. If voltage is still available from cruise fuse 3, voltage from STOP BCM Fuse 4 is supplied to sound the alarm through CKT 140 (ORN). Turn off the headlamp switch in order to turn off the alarm. The alarm module no longer senses voltage from the headlamp switch, so the alarm does not sound.