Restraints and Safety Systems: Description and Operation

System Description

SRS Components




The SRS is a safety device which, when used in conjunction with the seat belt, is designed to help protect the driver and passenger in a frontal impact exceeding a certain set limit. The system consists of the SRS unit, including a safing sensor and an impact sensor (A), the cable reel (B), the driver's airbag (C) and the passenger's airbag (D). The seat belt tensioner (E) is linked with the SRS airbags to further increase the effectiveness of the seat belt. In a front-end collision, the tensioner instantly retracts the belt firmly to secure the occupants in their seats.

SRS Operation
The main circuit in the SRS unit senses and judges the force of impact and, if necessary, ignites the inflator charges. If battery voltage is too low or power is disconnected due to impact, the voltage regulator and the back-up power circuit respectively will keep voltage at a constant level.

For the SRS to operate
1. The impact sensor must activate and send electronic signals to the microprocessor.
2. The microprocessor must compute the signals and send them to the airbag inflators (and seat belt tensioners).




3. The inflators must ignite and deploy the airbags (and activate the tensioners).

Self-diagnosis System
A self-diagnosis circuit is built into the SRS unit; when the ignition switch is turned ON (II), the SRS indicator comes on and goes off after about 6 seconds, if the SRS is operating normally. If the indicator does not come on, or does not go off after 6 seconds, or if it comes on while driving, it indicates an abnormality in the SRS. The SRS must be inspected and repaired as soon as possible. For better serviceability, the memory will store the cause of the malfunction, and the data link circuit passes on information from memory to the data link connector (DLC) 16P. This information can be read with the HDS connected to the data link connector (DLC) 16P.