Rick's Free Auto Repair Advice


Airbag know-how

Front driver and passenger airbags have been required on new vehicles since the 1999 model year. Side curtain airbags aren’t required, but most new car makers now install them the vehicle can meet federal side protection requirements.

Studies prove that front airbags reduce driver fatalities in frontal crashes by 29% and front-seat passengers by 37% for persons 13 years old and older.

How airbags work

Impact sensors located in the vehicle measure impact severity. Based on the impact severity, the airbag control module determines when to trigger airbag inflation. The inflation is timed so the driver or passenger hits the air immediately after the airbag has reached full inflation. That’s an important fact because you don’t want to hit an airbag while it’s still inflating. That can cause facial injuries.

The airbag controller knows if the driver and passenger have fastened their seatbelts and varies the airbag trigger timing accordingly. For example, the airbag will fire at a 10-12 MPH equivalent impact for unbelted passengers and around 16 MPH for belted passengers.

Airbags work hand in hand with seatbelts

Late-model vehicles have pre-tensioning devices built into the seatbelt retractor. A tiny explosive device triggers to wind the seat belt back in slightly (called pre-tensioning) to further secure the occupant before hitting the airbag.

Airbags, pre-tensioning explosive devices, and airbag controllers are one-time use devices

Once an airbag or seat belt pretension or has triggered, it cannot be reused. Neither can the airbag controller. All must be replaced with new parts.

Aim tilt steering wheel airbag towards your chest

Most vehicles are equipped with tilt steering wheels. While you may enjoy driving with the wheel tilted up, it’s safer to drive with the wheel airbag facing your chest. That way you ‘ll avoid the airbag hitting your face during an impact.

Airbag SRS light on

The technical name for an airbag system is the Supplemental Restraint System (SRS). It’s named that because airbags are designed to work in conjunction with seat belts. At each start, the airbag controller communicates with each crash sensor and each airbag. If the controller doesn’t get a response or an incorrect response from the component, it will light an SRS malfunction light.

Many DIYers think they can clear the SRS trouble code. But if you don’t fix the underlying cause, the SRS light will come back on during the next startup.

What Causes an SRS light?

Most often, SRS trouble codes set due to connector issues. Airbags use special yellow locking connectors. The connectors are sealed against moisture intrusion. But sometimes those seals fail and corrosion can set in, especially if you’ve had rainwater enter the vehicle and soak the carpet.

The first step in correcting an SRS light is to scan the computer to obtain the trouble code. In many cases, a communication problem can be fixed by disconnecting and reconnecting the yellow connector to the component. HOWEVER, you must depower the airbag system before disconnecting or reconnecting any airbag connector. The depowering procedure varies for each year, make, and model, so check the shop manual for the specific depowering procedure for your vehicle.

Driving with SRS light on

The airbag control module monitors how many times you’ve started the vehicle with the SRS light on. If you drive with the SRS light on, your airbags won’t work. If you or your passenger are injured in an accident where airbag inflation could have saved a life, don’t count on suing the carmaker; their butts will be covered by the data inside the controller showing that you knowingly drove the vehicle with an inoperative airbag.

Cracked windshields and airbags

Some carmakers locate the passenger airbag so it inflates upwards to hit the windshield before moving out towards the passenger. If your windshield has a crack, it may break and prevent the passenger airbag from inflating.

©, 2020 Rick Muscoplat


Posted on by Rick Muscoplat


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