The seat belt alarm is located in the truck body control module (TBC). The TBC is located under the center instrument panel sound insulator. Refer to Truck Body Control Module Replacement in Truck Body Control Module. For more information, refer to Audible Alarms in Electrical Diagnosis.

Some models use an audio alarm system in order to remind the driver to perform the following actions:

This system uses an alarm that sounds 3-5 times. The alarm activates a warning lamp on the instrument cluster when the ignition switch is turned to the RUN position and the driver's seat belt is not buckled. If the ignition switch is turned OFF and the headlamps are ON, then the TBC sounds (chimes) in order to remind the driver to turn OFF the headlamps. The alarm also sounds if the driver's door opens while the key is left in the ignition switch. If the instrument panel lamp dimmer thumbwheel is turned OFF and the headlamps are ON, the alarm does not sound if the ignition switch is turned OFF. The alarm module mounts to the convenience center.

The power distribution center is located at the right side of the steering column. The power distribution center is part of the instrument panel harness assembly. The following components mount to the power distribution center:

The relay center, also called the underhood bussed electrical center (UBEC), is located under the hood. The following components mount to the relay center:

The seat belt warning system switch is located in the seat belt buckle. The seat belt warning system switch provides ground when the buckle is not joined with the other part of the belt. When the belt is not buckled while the ignition is in the RUN position, the retractor switch closes and the alarm is activated.

The headlamp-on warning circuit activates when the headlamps are ON and the ignition is in one of the following positions:

The TBC senses voltage from the instrument panel dimmer switch and activates an audible warning. For more information, refer to Audible Warnings in Electrical Diagnosis.