Switch, passenger airbag (733)
| Switch, passenger airbag (733) |
| General |
A system for passenger airbag cut-off can be obtained as an option. The passenger airbag is disconnected with a switch, at which system status is indicated on the switch panel. Note that the switch is connected to the airbag control module and is not connected to the ignition circuit for the passenger airbag.
In order to increase reliability and enable diagnosis of the switch a resistor at 300 ohms is connected in parallel with the switch, and in series with the switch is a resistor at 100 ohms. The switch thus provides a total resistance of 100 ohms when it is closed and 400 ohms when it is open. This means that the airbag control module can detect a short circuit between the wires (very low resistance) or open circuit (infinitely high resistance) in the circuit and can distinguish this from the normally occurring values of 100 or 400 ohms. 100 ohms corresponds with a connected passenger airbag and 400 ohms with it cut-off.
The control module's input pin 13 has an AD converter and pull-up resistor to B+. The switch's resistance value of 100 or 400 ohms provides two well-defined voltage values on the AD converter's input. These are interpreted by the processor as switch position ON or OFF, all other voltage levels are interpreted as incorrect or unreasonable position in the switch.
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