Seatbelt reminder

Seatbelt reminder

The seatbelt reminder system monitors fastening of the driver and front passenger seatbelts.

The passenger seat contains a sensor which detects if the seat is occupied/loaded. Each seatbelt buckle has a switch which is connected to the airbag control module. If the seatbelt is not fastened, the control module sends a reminder that is indicated as follows:

•	seatbelt reminder lamp ”FASTEN BELTS”

•	audible signal (SID)

•	text message on the SID (certain markets only).

The seatbelt reminder lamp lights each time the ignition is turned ON and remains on until the belts are fastened.

Description of operation

The seatbelt reminder lamp lights when the ignition is in the ON position (+15 and +54) and when the driver or passenger has not buckled up.

The seatbelt switch (70D/70P) is closed when the seatbelt is not buckled up and open when the tongue is inserted.

The front passenger seat cushion has a load sensor. The passenger seat sensor (614P) is connected across pins 5 and 21 of the TWICE. The sensor is supplied with power via pin 5 and a resistor in TWICE, and grounded via pin 21.

The resistance of the sensor varies with the load. TWICE measures the voltage across the sensor. When the resistance of the sensor is lower than 50 kOhm, the seat is presumed to be occupied.

Burn-off

To ensure the best possible contact between the sensor connectors, the TWICE sends a voltage across pins 5 and 21 to burn off any oxide. This voltage is supplied for 1 second when the ignition is turned ON.

To ensure that the burn-off current is sufficiently high, there is a diode connected in parallel across the sensor connections. The resistance of the diode is low, which means that the burn-off current runs through the diode instead of the sensor.

Indication

The seatbelt reminder lamp (72) is supplied with +15 from fuse 26.

The reminder lamp is grounded via pin 15 of SID.

With the ignition ON the seatbelt reminder lamp illuminates and remains on until the driver and any front seat passenger buckle their seatbelts.

An acoustic signal sounds for 6 seconds or until the driver buckles his/her seatbelt (in certain markets this also applies for the passenger side).

If the seatbelt has not been buckled when the speed exceeds 25 km/h then "USE YOUR SEATBELTS" is shown in SID and the seatbelt reminder lamp flashes at the same time.

If the driver or passenger has still not buckled then a third reminder is given after a certain time in the form of an acoustic signal. This sound continues for a while and then stops.

The text in SID can be cleared with the steering wheel's CLR button.

The airbag control module sends a bus message and the SID emits an audible signal.

Diagnostics

If there is a fault in the seatbelt reminder lamp circuit, DTC B1210 is generated in TWICE. The DTC is generated in the event of:

•	An open circuit or short circuit to ground

•	A short-circuit to B+.

No diagnostic trouble code is generated for voltages below 11 V or during diagnostic communication.

Bus communication

Used information	Sensor system
Ignition +54 (On/Off)	DICE

DICE provides the system with information on +54.

Sent information	User System
Passenger seat occupied (yes/no)	ACC
Acoustic reminder (On/Off)	SID