Toyota Tundra Service Manual: System Description

Toyota Tundra Service Manual / Vehicle Interior / Seat Belt / Seat Belt Warning System / System Description

SYSTEM DESCRIPTION

1. SEAT BELT WARNING SYSTEM DESCRIPTION

(a) Driver seat belt warning light:

The seat belt warning light on the combination meter assembly illuminates, blinks or turns off in accordance with the driver seat belt state, vehicle speed, shift lever position and parking brake state.

(b) Front passenger seat belt warning light:

The seat belt warning light on the combination meter assembly illuminates, blinks or turns off in accordance with whether the front passenger seat is occupied, the front passenger seat belt state, vehicle speed, shift lever position and parking brake state.

After turning the ignition switch to ON, if the driver seat belt is not fastened within 1.8 seconds, check that the seat belt warning buzzer in the combination meter assembly sounds at 1.2 second intervals for 6 seconds.

When the vehicle is driven at 20 km/h (12 mph) or more with the front passenger seat occupied and the driver or front passenger seat belt not fastened, the seat belt warning buzzer in the combination meter assembly sounds once.

When 30 seconds have passed after the buzzer sounds, the seat belt warning buzzer in the combination meter assembly sounds at an interval of 1.2 seconds for 9.6 seconds.

After that, the seat belt warning buzzer in the combination meter assembly sounds at an interval of 0.4 seconds for 20 seconds.

2. FUNCTION OF MAIN COMPONENTS

Component	Function
Front seat inner belt assembly LH	Informs the center airbag sensor assembly of the driver seat belt condition (fastened or unfastened).
Front seat inner belt assembly RH	Informs the occupant detection ECU of the front passenger seat belt condition (fastened or unfastened).
Occupant classification sensor (Front LH / RH, Rear LH / RH)	Informs the occupant detection ECU of the front passenger seat condition (occupied or unoccupied).
Occupant detection ECU	Sends the front passenger seat belt buckle switch signal and occupant detection signal to the center airbag sensor assembly.
Center airbag sensor assembly	Sends the driver seat belt buckle switch signal to the main body ECU (driver side junction block assembly) via CAN communication. Sends the front passenger seat belt buckle switch signal to the combination meter assembly via CAN communication.
Main body ECU (driver side junction block assembly)	Sends the driver seat belt buckle switch signal to the combination meter assembly via CAN communication. Sends the parking brake switch signal to the combination meter assembly. Sends the parking brake condition to the combination meter assembly via CAN communication.
Brake actuator assembly (skid control ECU)	Informs the combination meter assembly of the vehicle speed signal.
ECM	Sends the shift position signal to the combination meter assembly via CAN communication.

Problem Symptoms Table

System Diagram

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