There is a driver seat belt reminder light on the instrument cluster.

When the vehicle is started, this light flashes and a chime may come on to remind the driver to fasten their seat belt. Then the light stays on solid until the belt is buckled.
This cycle may continue several times if the driver remains or becomes unbuckled while the vehicle is moving.
If the driver seat belt is buckled, neither the light nor the chime comes on.
Passenger Seat Belt Reminder LightDrive Range, Sixth Gear Automatic Transmission Unit
As the vehicle speed increases, the transmission control module-(TCM) receives inputsignals from the automatic transmission input and output speed sensors, the throttleposition sensor and other vehicle sensors to determine the precise moment to commandON the normally-low 26-pressure control solenoid ...