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Faulty Airbag Sensor? What To Do If Your Airbag Light Is On

Faulty Airbag Sensor

We’ve all been there. You’re driving down the road and suddenly a little red light pops up on the dash.

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Before you’ve had a chance to even figure out which light it is, your heart has jumped up into your throat and you're thinking “what’s this going to cost me?”.


It’s a pretty scary scenario, and whether your car’s airbag light is a little yellow man with a seatbelt on, or a bright red SRS symbol, it could well be pointing to a serious issue. SRS stands for Supplemental Restraint System, as is the official term for your vehicle’s airbag system.


Though it is usually okay to drive with this light on, it isn’t recommended. If you get into an accident you could find yourself without a working airbag. The best thing to do is to get your car checked and diagnosed as quickly as possible, as it could be one of several issues.

Why Is My Airbag Light On?

There are a number of reasons your airbag sensor light may be illuminated.

Your Airbag Backup Battery Is Depleted

Airbags need power to activate, and to make sure that in the event of an accident they actually do, they are hooked up to a backup battery.


If your car’s main battery has drained recently, it may well have depleted the airbag backup battery too. It may self-correct once the battery is fully charged again, if not, you may have to perform a sensor reset.

You Airbag Module Got Wet

If you’ve recently driven through floodwaters, or accidently left the window open in the rain, chances are the airbag module that sits under the driver’s or passenger’s seat got wet.


When this happens, it’s common for it to short out or corrode, causing the SRS light to come on.

Your Airbag Clock Spring Is Damaged Or Faulty

The airbag clock spring sits inside your steering wheel and basically keeps the electrical wiring between the car and the driver-side airbag from being damaged as the wheel is turned.

Over time, the airbag clock spring can become worn and damaged as a result of consistent turning of the wheel, which can trigger your airbag light.

One Of Your Airbag Sensors Is Faulty

Faulty airbag sensors are probably the most common cause of airbag lights coming on. 


Your vehicle has a number of different sensors which are designed to activate the airbag system in the event of an accident. Naturally, these can become faulty, which would cause the airbag light to illuminate.

Different Kinds Of Airbag Warning Lights

The two most common kinds of airbag warning lights are the letters ‘SRS’, or an image of a man with a seatbelt on and a deployed airbag in front of him.


Typically, these are either yellow or red, and stay illuminated.


However, some vehicles operate the light in different ways to communicate specific information back to you. For example, the light may be flashing, or it might alternate between blinking and being continuously on. 


It’s a good idea to refer to your vehicle’s user manual, as sequences such as these may be relaying info about a specific issue that you can attend to easily.

What Is An Airbag Sensor?

Your car has a number of airbag sensors, which can basically tell when the vehicle has been involved in an accident by sensing rapid deceleration. It can distinguish dangerous from non-dangerous collisions, and communicate with the airbag system to tell it whether or not to activate the airbags.


There are two main types of airbag sensors in modern vehicles.

Mass Sensor

Mass sensor systems are typically located in the front of the vehicle and measure impact. Usually there will be one sensor inside the engine and another somewhere in the passenger seating area.

Roller Sensor

Roller sensors have an internal coil spring component, which in the event of an accident experiences tension. This tension measures intensity of impact, communicating this back to the ECU to determine whether the airbags need to be deployed or not.

What’s All The Fuss About Airbags?

Airbags have been around since the late 1980s, and became standard equipment in all vehicles in 1998. Since their introduction, they have saved over 50,000 lives.


The location of your airbags ultimately depends on your vehicle, but these are typically located inside the steering wheel, and in the dashboard on the passenger side. Most modern vehicles also have rear passenger airbags, as well as seated-mounted and side-curtain airbags.


Short of wearing a seatbelt, airbags are one of the biggest contributors to safety during an accident, lowering accident death rates by around 30%


Where Is My Airbag Sensor Located?

The location of airbag sensors differs from car to car. The most common location is inside the front bumper or fender, however many modern vehicles have several airbag sensors.


They can also be found inside the engine bay, in the passenger seat area, or even in the rear or sides of the vehicle.

How To Reset Your Airbag Sensor

Often, all it takes to get rid of that pesky warning light is to reset your airbag sensor. This is a fantastic first step in diagnosing the issue if you don’t have a diagnostics tool. If the light comes back on after being reset, it’s a good indicator that your vehicle needs further attention.


The great thing about this step is that you don’t actually have to find the airbag sensor itself. If you have an OBD2 scanner handy, this is ideal, otherwise you can reset the airbag sensor by disconnecting and reconnecting the vehicle’s battery.


To do this, locate the battery under the hood (it might be in the trunk depending on your vehicle), and unscrew the nut on the negative terminal. The negative terminal is the one with the (-) next to it, (+) is positive.


Remove the terminal clamp and leave it disconnected for 5-10 seconds to allow the airbag sensor to reset. Then reconnect the battery terminal and turn the vehicle on. With a bit of luck, the light will stay off. If it comes back on then the best thing to do is to take your car in for a diagnostics scan.

How To Replace An Airbag Sensor

You shouldn’t go replacing airbag sensors willy nilly, so make sure you are 100% certain that a sensor is at fault before you buy a replacement part. Otherwise you could be pouring money down the drain. 


The best way to be sure that the issue is an airbag sensor and not something else (like airbag clock springs or a wet airbag module), is to connect a diagnostics tool to your car’s OBD2 port and run a full scan.


Once you’ve determined the issue is indeed an airbag sensor (and you know which one needs replacing), then you can get to work.


With the new part in hand, grab your manufacturer’s service manual and determine the location of the faulty sensor.


The specific steps will differ depending on your vehicle, and you should consult the service manual for any specific information regarding your make and model. Here’s a basic overview of the process:

1 – Keep The Engine Off

You don’t need the engine on for this job, and you certainly don’t want to get your hands or hair caught in anything. Leave the engine off.

2 – Disconnect The Battery

This one’s a super important step. If you fail to do this, you could inadvertently activate the airbag system, causing them to deploy inside your car.


That’s a surefire way to turn a simple and cheap repair job into a nightmare. Once the battery is disconnected, give it a few minutes before you begin.

3 – Grab All Your Tools

Having everything you need handy makes the process a lot easier. There’s nothing worse than having to climb out from under the vehicle because you grabbed a 10mm socket but not a 12mm. 


Read through all the steps here and in your manual, and keep everything you need nearby.

4 – Test The Sensor If Needed

If you still aren’t 100% sure if the airbag sensor is at fault, you might like to test it with a digital multimeter. The current output should be less than 10mA, though you should consult your vehicle’s manual for model specific info.

5 – Get That Sucker Out Of Here

Carefully disconnect any electrical connections from the module and move them aside. For front impact sensors, disconnect the 4P connectors from the driver and passenger side sensors.


You may need to unbolt the module depending on how it’s mounted. Now carefully remove the sensor and open up the new one.

6 – Replace With The New Sensor

Grab the new airbag sensor and carefully put it back in place. Reconnect all connections and mountings and you’re done!

7 – Wrap It Up

Reconnect the battery terminals and turn your vehicle on to see a beautiful, warning light-less dashboard! If the light doesn’t come off automatically, you might need to reset it with a scanner tool.

Airbag Sensor Replacement Cost

The cost of replacing your airbag sensor largely depends on the difficulty of the job itself. The parts are typically pretty inexpensive, however these are sensitive components, meaning the replacement process is pretty sensitive too.


It can easily take a couple of hours for even a professional mechanic to diagnose, remove and replace a faulty airbag sensor. Specialty and luxury vehicles can be even more complicated, pushing the labor cost up even further.


Airbag sensor replacements typically cost around $250-$350, and it’s generally recommended to have an expert mechanic complete the job, given how important and sensitive the repair is.


If you’re confident and comfortable with at-home repairs though, you can save a huge part of the replacement cost by not paying for labor. Depending on your vehicle’s model, an airbag sensor could be as little as $50, up to around $200 for most vehicles.


What You Should Do If Your Airbag Light Is On Now

First of all, don’t panic. It’s more than likely a simple repair such as an airbag sensor replacement.


You can still drive the vehicle, but you should bear in mind that there could be an issue with your airbag system. This could mean that in the event of an accident your airbags may not deploy.


So, it is something you should tend to fairly urgently. Most garages have a diagnostics tool and getting a scan is fairly expensive (and sometimes free of charge), so we’d recommend heading to your nearest workshop and getting the vehicle checked out.


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