TSB: Red Warning - Occupant Seat Belt not Fastened - March 1, 2024

[Tooney]

Condition
The customer complains of a red warning message in the instrument cluster that reads, “Occupant seat belt not fastened. Fasten seat belt.” This message appears despite all seat belts being fastened.

Technical Background
The red warning message may appear for one of three reasons:
1. The belt buckle is faulty,
2. The vehicle is moving at a speed greater than 18 mph (30 km/h) and an occupant does not have their seat
belt fastened, or
3. The vehicle detects improper use of the seat belt by the driver (e.g., use of a dummy belt buckle).

The airbag control unit (CU) counts the number of drive cycles where the seat belt is not disconnected after the cycle is complete (i.e., the vehicle is shut off). Once the threshold of 5 cycles is reached, the warning light shown in Figure 1 appears in the instrument cluster.
Note: The count is decreased by 1 each time that the seat belt is disconnected after a drive cycle. Therefore, more than 5 drive cycles may be required to set the red warning in the instrument cluster.
https://static.nhtsa.gov/odi/tsbs/2024/MC-10252433-0001.pdf

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[Racer_Ex]

Condition
The customer complains of a red warning message in the instrument cluster that reads, “Occupant seat belt not fastened. Fasten seat belt.” This message appears despite all seat belts being fastened.

Technical Background
The red warning message may appear for one of three reasons:
1. The belt buckle is faulty,
2. The vehicle is moving at a speed greater than 18 mph (30 km/h) and an occupant does not have their seat
belt fastened, or
3. The vehicle detects improper use of the seat belt by the driver (e.g., use of a dummy belt buckle).

The airbag control unit (CU) counts the number of drive cycles where the seat belt is not disconnected after the cycle is complete (i.e., the vehicle is shut off). Once the threshold of 5 cycles is reached, the warning light shown in Figure 1 appears in the instrument cluster.
Note: The count is decreased by 1 each time that the seat belt is disconnected after a drive cycle. Therefore, more than 5 drive cycles may be required to set the red warning in the instrument cluster.
https://static.nhtsa.gov/odi/tsbs/2024/MC-10252433-0001.pdf

Interesting. I recently had a similar problem that took the dealer a week to figure out. In my case, however, the seat belt indicator warning would go off when there was NO one sitting in the seat. The dealer initially tried replacing the buckle, which made no sense given that it wasn't in use. Eventually they found a faulty connection to the sensor. Idk it took a week to figure that out.

This was the second faulty connection causing issues, on a 2024 Turbo S. The first one was the external temperature sensor, which also caused the TPMS and one park assist sensor to malfunction. That one also took about a week to diagnose and fix.