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Seat belt warning

Seat belt warning





The seat belt warning checks that the driver and front-seat passenger have fastened their seat belts.

The passenger seat has a sensor that detects when the seat is occupied/loaded. Each buckle has a contact connected with TWICE. If the belt is not fastened, TWICE sends a warning, which is indicated in the following way:


• belt warning lamp ”FASTEN BELTS”

• acoustic signal (SID).


The belt warning light is turned on each time the ignition is turned ON and stays alight until the seat belt is fastened.

Description of operation

The belt warning light is turned on when the ignition is ON (+15 and +54 circuits) and when the driver's or front-seat passenger's seat belt is not fastened.

The belt contact (70D/70P) is closed when the seat belt is not fastened, and open when it is.

The front passenger seat cushion contains a sensor which detects load. The passenger seat sensor (614P) is connected across pins 5 and 21 of TWICE. Voltage is supplied to the sensor from pin 5 via a resistor in TWICE, and pin 21 is grounded.

The resistance of the sensor varies depending on the load exerted on it. TWICE detects the voltage across the sensor. When the resistance is below 50 kOhm, the load on the seat is considered to mean that it is occupied.

Burn-off

To maintain the best possible contact in the sensor connections, TWICE sends a voltage across pins 5 and 21 to burn off any oxide. This is done for 1 second with the ignition ON.

To ensure that the burn-off current remains sufficiently high, a diode is connected in parallel across the sensor connectors. The diode conducts at low resistance, which means that the burn off current passes through the diode instead of the sensor.



Indication



The seat belt warning light (72) is turned on via +15 circuit from fuse 27.

The warning lamp is grounded via pin 28 in TWICE.

The belt warning is also given in the form of an acoustic signal. the signal is given for 6 seconds if a seat belt is not fastened. When the belt is fastened, the acoustic signal stops.

TWICE sends out an acoustic warning (On) to the bus and the SID unit gives an acoustic signal.

Diagnostics

If there is a fault in the belt warning lamp circuit, diagnostic trouble code B1210 is generated in TWICE. The trouble code is generated if there is:


• An open circuit or short circuit to ground

• A short-circuit to B+


The diagnostic trouble code is not generated when the voltage is below 11 V or during diagnostic communication. The control module output can be activated with the diagnostic tool.

Bus communication

Information used

Sensor system

Ignition +54 (On/Off)

DICE





DICE supplies the system with information on +54 circuit.

Information Sent

User system

Passenger seat occupied (yes/no)

ACC

Acoustic warning (On/Off)

SID