Toyota ST185 Series Repair Manual page 128

SRS AIRBAG
The airbag system has connectors which possess the functions described below:
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1. AIRBAG ACTIVATION PREVENTION MECHANISM
Each connector contains a short spring plate. When the
connector is disconnected, the short spring plate
automatically connects the power source and grounding
terminals of the squib to preclude a potential difference
between the terminals.
2. ELECTRICAL CONNECTION CHECK MECHANISM
This mechanism is designed to electrically check if
connectors are connected correctly and completely.
The electrical connection check mechanism is designed so
that the connection detection pin connects with the
diagnosis terminals when the connector housing lock is in
the locked condition.