What to do When Your Airbag Light is On

Your airbag light might come on unexpectedly for three reasons:

1. There's a problem with your airbag and it cannot properly deploy.
2. The airbag already deployed but was not properly reset.
3. There is a computer or electrical problem in the dashboard and the light came on accidentally.

Either way, you should take your car to a mechanic as soon as possible. An active airbag light means your supplemental restraint system (SRS) will not work in the event of a collision.

How Your Airbag Light is Supposed to Work

Every time you start your car, the computer checks all of the vehicle's systems to make sure they're working properly and that you can drive safely. Lights on the dashboard come on as the checks are in progress and go off once everything is cleared. If a light starts blinking and doesn't shut off, this is a sign that something is wrong.

If you see the airbag light on your dashboard, have a mechanic take a look as soon as possible.

Checking the Airbag Warning Light

There are two ways to figure out why your airbag light won't shut off. One is to take the vehicle to a mechanic to run a diagnostic on the car's airbag electronic control unit (ECU). This computer stores data about all of your vehicle's processes and provides a code that alerts auto technicians to any issues.

You can also understand the problem yourself by counting the number of times your airbag light flashes before stopping for a brief period of time. The number you arrive at will range from 12 to 53 and corresponds to an airbag code. Differences may occur among manufacturers, but the most common codes are:

Code 12: Low battery voltage
Code 13: Airbag circuit is shorted or grounded
Code 14: Short or ground on the primary crash circuit
Code 21: Airbag is mounted improperly
Code 22: Safing sensor output shortage
Code 23: Safing sensor input feed or return circuit open
Code 24: Open output feed
Codes 32 to 35: Problems with the driver and passenger side airbags
Codes 41 to 45: Problems with the left and right primary crash sensors

The airbag module must be reset or replaced after the bags deploy. After fixing any issues with your safety system, an auto technician will clear any airbag codes on the ECU so your light will go off. This also reactivates the SRS.

How the Airbag System Works

The SRS is one of several measures designed to keep travelers safe on the road. It works in conjunction with the seatbelt to keep you firmly in your place during an accident, preventing you from flying through the windshield or slamming into the steering wheel. When a collision occurs, your car's computer and sensors kick into gear and deploy the airbag within milliseconds.

1. Collision sensors in your car determine that an accident has occurred. These sensors are triggered by increased pressure, sudden stopping, an increase in break pressure and other factors.
2. These sensors send a signal to your car's airbag module.
3. The vehicle's seatbelts - and sometimes windows - lock. The airbag ECU calculates whether or not the SRS is necessary based on the data it received.
4. If the accident is severe enough, the ECU signals the inflator system. This sets off a chemical charge.
5. The reaction produces gas that fills the airbag and causes it to expand past the car's paneling. Many believe airbags inflate with air, but it's actually nitrogen.
6. After the airbag deploys, it must be replaced by a mechanic as soon as possible. It's best to have a new airbag before you resume driving the vehicle.

More Reasons Why Your Airbag Light Comes On
Have you ever wondered why airbags don't go off in newer vehicles if a small child or a bag is in the front passenger seat? That's because the system is sensitive to weight. The front passenger seat has sensors to detect if there's someone occupying the area. If there isn't, or if the person is so small he or she could get hurt from the force of an airbag, the system will shut off and a light on the dashboard that reads "Passenger Airbag Off" will come on. The light will disappear when someone bigger sits in the seat. If the passenger seat's sensors are worn or disconnected, however, this light won't work correctly.

A drained battery can also cause your airbag light to come on unexpectedly. You'll need to charge or replace the battery and then reset the ECU.

Another indication that there's something wrong with an airbag system is if the light is on and the horn won't work. This is a sign that your clock spring needs replacing. This piece connects the driver-side airbag with the rest of the car's electrical wiring and reacts as you turn the steering wheel. The spring becomes worn after years of use, disrupting the connection between the airbag and the wiring.

Water damage could also be the cause of an airbag light. Many cars house their airbag modules under one of the front two seats. These can be damaged by even a small amount of moisture.

Don't worry if you're unable to diagnose these conditions yourself. Each one transmits a code to the ECU that tells your mechanic exactly what's wrong with the vehicle.

Additional Things to Consider

Airbags provide a great deal of protection, but they can be dangerous. If the steering wheel is tilted incorrectly, an accident can cause the airbag to deploy straight in your face and smother or injure you. Be sure the wheel is angled toward your chest, not your face, and that you sit about 10 inches away.

A History of the Airbag
The first airbag wasn't invented until the middle of the 20th century. Before then, drivers were left completely unprotected. Car accidents resulted in greater injuries and a higher number of deaths. Survivors often suffered from facial mutilations after slamming into the dashboard or steering wheel. Automotive Engineer Magazine noted that doctors nicknamed the effects of these accidents "steering wheel faces."

In the spring of 1952, John Hetrick was driving through Pennsylvania with his wife and child in a 1948 Chrysler Windsor. As the family came to the top of a hill, they suddenly saw a large rock in the road. Hetrick slammed on the brakes and jerked the car to the right to avoid it but ended up taking the car into a ditch. The two parents had to hold their child back to prevent her from hitting the front of the car. The action saved the child's life.

The accident left Hetrick troubled but curious. He kept imagining a device within the car itself that could do what he and his wife had done: shield a person from impact. Hetrick began sketching designs for a safety measure consisting of an inflatable cushion, an air accumulator and a release valve. He filed for a patent that August.

Other inventors and businesses in the automotive industry began designing similar safety features. Among them was German inventor Walter Linderer, who received a patent for a safety cushion shortly after Hetrick. However, the challenge for car manufacturers was to install a system that could detect a car crash and deploy quickly enough to protect passengers from harm. In addition, the bags couldn't inflate with too much force, lest they ended up injuring people themselves.

In 1969, however, President Lyndon B. Johnson called for all cars in the U.S. to come with "automatic occupant protection systems."

Mercedes-Benz had already begun developing airbags for its vehicles two years earlier. However, it wasn't until 1968 that the most important piece of the airbag system was invented: the sensor. Allen K. Breed, a mechanical engineer from New Jersey, created an inexpensive, reliable device that revolutionized car safety and paved the way for every manufacturer to install airbags.

Your airbag is a vital part of protecting you and your passengers during travel. As such, traveling while the airbag light is on means you and anyone in your car is at an increased risk of injury if an accident occurs. Because the SRS is so important, it's best to have it checked out by an experienced professional if it requires repair.