Supplemental Restraint Systems Overview
Airbag Technology for 2010
The cars being manufactured today are a far cry from those made in the 20th century ... especially when it comes to safety systems. The entire automobile has been redesigned from top to bottom with passenger safety top of mind. What once was merely a lap safety belt is now a restraint system with as many as 12 airbags, explosive seat belt pretensioners and accident detection systems. The world of airbags and restraint systems is constantly changing.
Airbag Systems Today
Most vehicles being produced this model year will have the following components as a base safety restraint system:
• driver's airbag
• passenger's airbag
• front seat belt pretensioners
• side curtain airbags
• seat airbags
• remote sensor(s)
• control unit
• passenger seat sensing system
Some common misunderstandings about airbags are: 1) To reset the airbag light, just unplug the battery and wait a couple of minutes, or 2) The clockspring needs to be replaced every time the airbag goes off. Both of these concepts are wrong.
Understanding that every vehicle is different is the first correct assumption one can make. There are classes offered by colleges, technical schools and car manufacturers available to those seriously interested in learning how to service and repair these systems properly. Entry-level two-hour seminars only touch on the generalities of each system and although participants leave with a certificate, the learning has really just begun.
Estimating is still a "visually-based method" relying heavily on the individual appraiser. If it looks damaged, find it in the database and click it into the estimate. But when it comes to supplemental restraint systems (SRS), the truth is that this is the only system in the vehicle that has clearly spelled out criteria and component replacement requirements. Whether it's a front deployment consisting of one seat belt pretensioner and one airbag, or a complete side hit deploying both the curtain and the seat airbag, the rules for component replacement are well defined by each manufacturer.
Information Service Providers
Most estimating systems provide pencil sketches, H notes, P pages and matrix charts leaving the choice of components in the hands of the appraiser. Each writer still needs to interpret the necessary replacement components based on what he or she sees and how they read those notes and charts. The information used is critical to a successful repair. Here is an alphabetical list of the different information service providers (ISPs).
• AirbagSolutions.com - a pictorial database providing OEM requirements and locations for airbag replacement and service following a deployment (actual component photos)
• Alldata - step-by-step replacement instructions for many airbag components (some pencil sketches included)
• Audatex - a descriptive matrix (list) of items to inspect and replace following an accident with an airbag deployment
• CCC/Pathways - a drop-down list of items to inspect and replace following an accident with an airbag deployment (component pencil sketches)
• Mitchell International - component descriptions, step-by-step replacement instructions and a matrix for replacement items (text and pencil sketches)
Although each manufacturer has unique rules for powering down a restraint system, a good rule of thumb (including hybrids) is "always disconnect the battery, remove all powered devices, such as cell phones, iPods or memory savers from their cradles and wait 10 minutes before working on any restraint system." Every vehicle has a reserve battery power circuit designed into the system to ensure a restraint deployment even if the battery is damaged or becomes disconnected during the crash event. These capacitors retain battery power for up to 10 minutes after disconnecting the battery. Furthermore, it takes less than 9 volts to deploy an airbag or pretensioner, so even the current from a cell phone recharging in the cradle could supply enough power in the circuit to accidentally deploy an airbag.
• Driver's airbags are held in place by either bolt-on fasteners or spring loaded clip-in fasteners. Bolt-on airbags require you to simply identify the type of bolt used, remove it and release the airbag from the steering wheel. Spring-loaded, clip-on designs can get more difficult and may require special tools. Releasing the spring mechanism is often challenging and sometimes difficult.
• The clockspring is nothing more than an extension cord from the dash harness to the driver's airbag providing a constant electrical connection to the airbag. Many manufacturers require clockspring replacement after a deployment, while others do not. The most common problem with a clockspring is that they may melt during the airbag deployment, making reuse impossible. This component should never be repaired.
• Passenger airbags have two designs; those with a cover and those without. Most passenger airbags with a cover do not require the removal or replacement of a dashboard and can usually be accessed and removed through the glove box. Those without a cover require much more work and expense, often involving a complete instrument panel overhaul and/or replacement. Having the proper tools and experience is critical to replacing this type of airbag.
• Control units are the most critical component to the restraint system. These "brains" of the system determine which component will be deployed during any crash event. It is also responsible for the continuous monitoring of the entire restraint system and will illuminate the airbag light anytime a component or connection is not returning the proper signal. Each manufacturer has its own rules regarding reuse or replacement of this component following a deployment. Some require control unit replacement and are "plug and play" while others require reprogramming, downloading from the dealer or configuration before they are fully activated. Others may allow multiple crash events before requiring replacement. These units are located throughout the vehicle in such places as under either front seat, inside the console, under the radio, in the kick panel, or behind a heater box. Each manufacturer is different.
• Seat belt pretensioners are designed to pull the "at-risk" occupant back into position milliseconds before the airbags deploy, thus creating a safer airbag deployment. Some manufacturers use a pretensioner in the belt, some use it in the buckle and some use both. Often a manufacturer will require all the seat belts (and components) be replaced following a deployment. Some systems allow seat belt pretensioners to deploy independent of the airbags, while others still deploy together. Many of the newer vehicles will deploy individual components as determined by the control unit (e.g. driver's airbag, passenger's seat belt pretensioner).
• Seat airbags also have multiple designs, bolt-on external modules and internal designs. Those with an internal design require either full seatback replacement or full seatback overhaul with seat component(s) replacement. This aspect of seat repair is often mistaken for an easy and fast way of cutting a corner to save money. No manufacturer allows the repair of a seat cover following a deployment. They all require seatback or seatback cover replacement. With the high cost of some seat covers, this can be a tempting mistake. The thread and stitching used for a seatback cover with a side airbag is unique. Following proper procedure is critical for a safe future deployment. Improper assembly or stitching could result in a failed or altered future deployment, causing serious consequences.
• Curtain airbags, mounted along the roofline, also have specific criteria following a deployment. While some manufacturers allow the replacement of the curtain alone, others require a new headliner, upper trim panels, new grab handles, sun visors and even coat hooks.
• Occupant Classification Systems (OCS) are the most recent addition to the ever-changing safety systems. These sytems help the airbag control unit determine how to deploy the passenger airbag, based upon the weight and size of the occupant of that seat. Recalibration following a deployment may require using a set of weights and a factory scanner, while others may require a recalibration during a "road test." Seat systems may use track-mounted ceramic sensors or a bladder or weight sensor in the seat bottom cushion. It is important to understand which system you have before removing or replacing a passenger seat.
• Tools and scanners
Do you think you have what you need to service and reset these systems? Think again. Although the DLC connector has made most vehicle diagnostics uniform, the airbag systems are still outside that box. The computer used for airbag codes is different from the computer used for the check engine light. Almost every vehicle requires a scanner specific to airbags or an interface with software unique to that car and system. If you want to be able to read and reset the airbag light on every vehicle, be prepared to spend between $40,000 and $50,000, knowing that annual updates for each one will still be required.
Learning all the proper procedures and specific requirements for these systems makes both estimating and repairing these systems easier and leads to a more successful repair.
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