Supplementary Restraint System (SRS) (Description and operation)

Supplementary Restraint System (SRS)

SRS Description

The Supplementary Restraint System (SRS) provides additional protection for front seat occupants during a frontal collision above a preset severity.

The system is operational only with the ignition switch in position II. With the ignition on, any frontal collision is detected by an accelerometer and a mechanical safing sensor within the airbag DCU. If the impact is above the preset severity, the airbag DCU transmits simultaneous signals to fire the airbag modules and seat belt pretensioners. The airbag modules deploy protective airbags in front of the driver and front seat passenger and the seat belt pretensioners retract to tighten the front seat belts.

The airbag DCU can store fault codes for the DCU, the driver and passenger airbag modules and the pretensioners. These fault codes can be accessed using TestBook/T4 via the diagnostic socket.

The airbag DCU is located below the centre console near the handbrake mounting. The driver airbag is located in the centre of the steering wheel and the passenger airbag is located in the fascia, above the glovebox. The seat belt pretensioners are located with the seat belt anchorages.

An SRS warning LED is located in the instrument pack. When the ignition switch is turned to position II, the LED will be illuminated for 3 to 5 seconds to confirm LED operation. If a fault in the SRS system occurs, the LED will be illuminated for the duration of the fault or for a period of between 8 to 16 seconds.

The airbag DCU can supply a low voltage test current to the airbags and pretensioners to check circuit continuity. The DCU can also detect shorts, shorts to ground or battery and open circuits. These conditions can be retrieved using TestBook/T4.