General description and operation of airbags (Chevrolet Captiva 1)

Supplementary Inflatable Restraint System (SIR)

The Supplemental Inflatable Restraint System (SIR) is a safety feature used in combination with seat belts. The SIR does not replace the seat belt. The driver and passengers must always wear properly adjusted seat belts.

The airbag system is designed to protect the driver and front passenger in the event of a severe frontal vehicle collision. The airbags deploy when the applied force is within 30 degrees of the vehicle's centerline.

The airbag system consists of the following components:

• Driver airbag module
• Driver side airbag module
• Driver's curtain airbag module
• Passenger airbag module
• Passenger side airbag module
• Passenger curtain airbag module.
• Driver and front passenger seat belt tensioners (some models also have a load limiter).
• Sensor and Diagnostic Module (SDM)
• Clock spring.
• Wiring harness and connectors.
• AIRBAG indicator on the dashboard.
• Side airbag sensor

Airbag modules

Driver airbag module

Warning! Opening the driver's airbag module may result in injury due to unexpected deployment. Therefore, disassembling the driver's airbag module is prohibited.

The driver's airbag module is located under the center pad of the steering wheel. The driver's airbag module contains the initiator charge and the gas generator for inflating the folded airbag.

Passenger airbag module

Warning! Opening the passenger airbag module may result in injury due to unexpected deployment. Therefore, disassembling the passenger airbag module is prohibited. The passenger airbag module is located on the passenger side of the instrument panel. The passenger airbag module contains the initiating charge and the gas generator for inflating the folded airbag.

The passenger airbag module is located on the passenger side of the instrument panel. The passenger airbag module contains the initiator charge and the gas generator for inflating the folded airbag.

Side airbag module

Warning! Opening the side airbag module may result in injury due to unexpected deployment. Therefore, disassembling the driver's airbag module is prohibited.

The side airbag modules are located in the driver and passenger seats. The side airbag module contains the initiating charge and the gas generator for inflating the folded airbag.

Curtain airbag module

Warning! Opening the curtain airbag module may result in injury due to unexpected deployment. Therefore, disassembling the curtain airbag module is prohibited.

The curtain airbag modules are located in the roof rail from the front to the rear pillars. The curtain airbag modules contain the initiating charge and the gas generator for inflating the folded airbag.

Front seat belt tensioners

Warning! Opening the belt tensioner may result in injury due to unexpected activation. Therefore, disassembling the driver's airbag module is prohibited.

Seat belt tensioners (with load limiter in some vehicles) are installed on all front seat belt buckles to retract the seat belt buckle if a frontal collision is detected. The seat belt pretensioners are controlled by the sensing and diagnostic module (SDM). The seat belt pretensioner contains an initiating charge and a gas generator to retract the seat belt buckle. After a crash that causes the seat belt pretensioner to deploy, the pretensioner must be replaced.

Sensor and Diagnostic Module (SDM)

Attention! Handle the Sensor and Diagnostic module (SDM) very carefully during maintenance. Do not hit or shake the SDM. Never connect power to the Airbag Inflator system (SIR) unless the SDM is rigidly connected to the vehicle. All SDM module mounting bolts and ground nuts must be fully tightened. Failure to follow these precautions may result in a fire hazard and personal injury.

The Sensing and Diagnostic Module (SDM) is located on the floor beneath the floor console assembly. The Sensing and Diagnostic Module (SDM) performs the following functions:

• Monitors the electrical status of the Supplemental Inflatable Restraint (SIR) system components and sets a diagnostic trouble code (DTC) if a malfunction is detected.
• Records data about all detected problems.
• When the diagnostic device is connected, it displays diagnostic trouble codes for the inflatable airbag system (SIR) and system status information.
• Turns on the airbag warning light to alert the driver to a malfunction.
• Provides a backup power source to deploy the air bags and seat belt pretensioners if normal electrical power is interrupted as a result.
• Monitors vehicle speed by detecting frontal collisions that require airbag deployment.
• Passes electrical current through the airbag modules and seat belt pretensioners, activating them if a frontal collision of sufficient force is detected.

The Sensing and Diagnostic Module (SDM) does not contain any repairable parts.

Airbag warning light

The instrument cluster contains an airbag warning indicator that is related to the sensing and diagnostic module (SDM). The SDM performs an initial check when the ignition is turned to the ON position.



The SDM turns the airbag indicator light on and off seven times, connecting and disconnecting the ground in the indicator light circuit. If no malfunction is detected, the airbag indicator light turns off after flashing seven times.

If the Sensor and Diagnostic Module (SDM) detects problems in the internal or external electrical circuits that may adversely affect the operation of the inflatable airbag system (SIR), the airbag warning lamp remains lit. Some problems may cause them to fail to trigger when necessary, or to trigger when they are not normally required.

If the sensing and diagnostic module (SDM) is not connected properly to its connector, the airbag circuit is shorted to ground because there is a shorting jumper in the SDM electrical connector. This jumper is open when the connector is properly connected, but if the connector is not connected properly, the SDM connector bypasses the SDM and grounds the airbag indicator, causing the airbag indicator to remain illuminated.

Clock spring

Caution: Disassembling the clock spring may result in injury or damage to the clock spring.

Caution! Excessive winding of the clock spring (more than 3 and a quarter turns in one direction) without the steering wheel installed, this may result in damage to the clock spring and the inoperability of the driver's airbag.

The steering column contains a spiral element, which is called a clock spring due to its external resemblance to a mechanical watch spring. It is prohibited to disassemble the clock spring; it has nothing to do with measuring time. The clock spring contains two or three conductive spiral elements. One of the spiral elements provides a constant connection to the driver's airbag circuit, regardless of the steering wheel rotation. The clock spring also contains spiral elements that maintain constant contact with the horn and the remote control circuit.

When you turn the steering wheel one way, the spring tightens, and when you turn the steering wheel the other way, it loosens. Do not turn the clock spring when the steering wheel is not installed. For information on how to install the clock spring correctly, see Chapter "Clock Spring" in this section.

The clock spring also includes wiring and connectors for the horn circuit and the driver airbag circuit. The clock spring wiring connects to the yellow two-way connector on the bottom of the steering column.

Wiring Harness Connectors

If the sensing and diagnostic module (SDM) electrical connector is poorly connected, a built-in shorting jumper connects the wire from the air bag indicator lamp to the ground wire of the SDM module. This causes the air bag indicator lamp to turn on.

The short-circuit jumper is only an additional safety device. Always disconnect the Airbag Inflator system (SIR) before starting any maintenance procedures.

Passenger Seat Belt Reminder (SBR) Sensor

The seat belt reminder sensor detects the presence of a seated occupant and allows the sensing and diagnostic module (SDM) to control the occupant seat belt reminder indicator or chime.

The SBR sensor monitors the passenger seat pressure profile and sends it to the SDM. If the occupant's weight is higher than the specified value, the SBR sensor recognizes the presence of the passenger.

If the presence of an occupant is detected but the passenger seat belt is not fastened, the SDM turns on the passenger warning indicator.

If the presence of an occupant is not detected, the passenger warning indicator is switched off regardless of whether the seat belt is fastened or not.

For information on the status of the seat belt reminder, see "General Description" in Section 8A, Seat Belts.

The SBR sensor is not a repairable unit and should therefore be replaced together with the passenger seat cushion assembly.

(The article is reprinted from the website: ChevyMan.ru)