PRE-RELEASE
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:
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belt warning light ”FASTEN BELTS”
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acoustic signal (SID).
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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 sensor resistance varies according to the load it carries. TWICE detects the voltage across the sensor. When the sensor resistance is less than 50 kohm, the load on the seat is considered to correspond to a person sitting on the seat.
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 the +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:
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An open circuit or short circuit to ground
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A short-circuit to B+
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No diagnostic trouble code is generated for a voltage below 11 V or during diagnostic communication. The control module output can be activated using the diagnostic tool.
| Bus communication |
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Information used
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Sensor system
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Ignition +54 (On/Off)
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DICE
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DICE supplies the system with information on the +54 circuit.
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Information Sent
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User System
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Passenger seat occupied (yes/no)
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ACC
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Acoustic warning (On/Off)
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SID
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