Airbags play a critical role in keeping you as safe as possible during a collision. Airbags also deploy with an enormous amount of force. This means you want the airbag to come on only when it truly needs to come on to keep you safe during an accident.
This important task falls to your car’s airbag sensors, which instantaneously read impact forces firing all the airbags or the most appropriate airbags for the situation.
If an airbag sensor goes bad, it might deploy at the wrong time or not at all. Most modern cars are equipped with airbag warning lights that will flash or flicker anytime there’s a problem with the airbag safety system. Though there are other signs of an airbag sensor failure that you need to be keen to keep an eye out for.
What Does an Airbag Sensor Do?
An airbag sensor is engineered to detect moments of rapid deceleration that typically only occur during a collision. It works in tandem with your car’s computer and other safety components to tell the airbags to deploy. In some sophisticated vehicles, this can be used to strategically deploy only one or two airbags rather than activating all of them at once.
The airbag sensor actively monitors and detects the intensity of a collision to determine whether the airbag should be deployed or not. This is typically set at a tolerance level beyond what could be achieved by even the hardest braking.
Can an Airbag Sensor Go Bad?
It’s possible for the passage of time, electrical issues, battery problems, and bad airbag clock springs to cause your airbag sensor to go bad. It’s also possible for a past accident to have affected the airbag sensor causing it to fail with little to no warning.
What Causes Airbag Sensor Failure
There are a few things that can cause your airbag sensor to fail or prevent the airbag safety system from operating normally.
1. A Depleted Battery
Airbags need around 9 volts to function properly and deploy. If the system isn’t receiving sufficient voltage due to a bad battery or the alternator failing to charge the battery, the airbag sensor might not be able to function properly. Though some newer cars have emergency battery backup systems, many vehicle safety systems will turn on the airbag warning light when the system is underpowered.
2. A Faulty Airbag Module
If the airbag module has been damaged or has a loose wiring connection from corrosion, it can affect the airbag sensor. This is even more likely to be the case if you have an older car or you’ve recently been in an accident.
3. Bad Airbag Clock Springs
A problem with the airbag clock springs in the steering wheel can also cause the airbag sensors to fail. Sometimes it’s that the clock springs are defective. Other times it’s vehicle age or wear and tear. The problem is that the clock springs are deep inside the system where you can’t possibly see them. The only thing you get is the airbag warning light coming on, leaving you guessing.
4. A Fault in the Airbag Control Module
If the airbag control module has been damaged or suffered from internal corrosion after exposure to moisture, it can also affect the performance of the airbag sensors. This is also a common problem if you’ve recently had an accident that might have caused one or two but not all of your airbags to go off.
5. A Recent Accident
If you’ve recently had a minor fender bender that didn’t set off the airbags or maybe only set off one or two of your airbags, it can cause a fault in the airbag sensor. This is why it’s so important to have your airbag module reprogrammed or replaced after an accident, regardless of the damage’s severity.
Symptoms of a Failing Airbag Sensor
A lot of the mechanical symptoms of a failing airbag sensor are hard to spot on your own. The most obvious is the airbag warning light coming on in the dash display. Though cracks in an airbag from a recent accident or the vehicle’s interior getting wet could also be signs that your airbag sensors aren’t functioning properly.
1. The Airbag Light Stays On
It’s natural for the airbag light to flash momentarily when you first start the car, but if it stays on, the system is trying to alert you to a fault, which could include a bad airbag sensor. Every time you start your car, the computer checks all the various onboard systems.
Just like how your brake and ABS lights might flash for a moment, your airbag light will also flash. With some newer models, it will flash twice, with a pause, and then flash a third time as the car’s computer goes through the diagnostic cycle.
If the diagnostic check finds a problem with the ABS sensor, the car’s computer will keep the light on. However, this could be any one of several components or multiple airbag sensors.
2. The Airbag Light Doesn’t Flash at Startup
Conversely, if the airbag light doesn’t flash when you start the engine, then there is likely also an electrical fault, which could affect the airbag sensors. While this is rare, it’s often a sign that something is wrong with the car’s battery or other wiring connections in the console that is preventing the computer from testing the airbags.
3. Airbag Sensor Location
The most common place you find airbag sensors is in the front of the car where it serves as an impact sensor. They’re often attached to the radiator support. This makes sense as it’s where collisions are most likely to happen and where the most force will be applied. Some cars also have additional airbag sensors installed deeper in the engine bay.
Many cars these days come with side impact sensors that also monitor the intensity of impacts and measure pressure changes to determine if the door/side airbags should deploy. They’re built into the doors. Getting at them can be fiddly, as you have to tear apart the interior panels, which isn’t always easy.
So, if your airbag warning light comes on and stays on, you’ll also have to determine which airbag sensor or sensors are having a problem. If you’re not sure how many airbag sensors you have or where they’re located, you can usually find that information in the owner’s manual or the repair guide for your make and model.
Finding Which Airbag Sensor Is Failing
If the airbag warning light comes on, it might also throw one of the following codes to help you determine which airbag(s) are having a problem. Though you’ll usually need to put the key in the second position to power up the accessories, you’ll need a code reader that can read airbag codes like the Launch OBD2 Scanner CReader 6011.
Testing the Airbag Sensors
Testing the ohms with a multimeter is the most reliable way to test your car’s airbag sensors. Though first, you need to find and remove them, which isn’t always a straightforward proposition. Checking your owner’s manual or repair guide will give you a good idea of where they’re located.
Once you can access the airbag sensors easily, you can disconnect and test them via the following steps.
If this is tricky to do with two hands, you might want to support the airbag sensor in a small shop or vice lightly.
Airbag Sensor Replacement Cost
Replacing a bad airbag sensor on your own is possible to save some money. Though the obvious concern here is that if you get something wrong, the airbag could go off at the worst possible time. The flip side is that the biggest cost is the replacement airbag sensor.
A new airbag sensor will range from $75 to as much as $300, with a real-world average of around $150.
The labor cost to have a mechanic install it properly sits around $100 to $150. However, it might be a little higher if they need to open up the panels to access the malfunctioning airbag sensor, such as in the dash or deep inside one of the door panels.
When you consider that it’s a critical safety feature that you don’t want going off at the wrong time, the wise move might be to have a mechanic handle this type of repair for an average cost of around $225 to $350.
Frequently Asked Questions
Do I need to reset or reprogram my airbag control module after a collision?
If you suffered a collision that caused any airbags to go off, or you notice your airbag light staying on after a recent fender bender, the wise move is to take it in to have the airbag control module reset. Otherwise, it might not work the next time when you truly need it. This might also require replacing any bad airbag sensors that were affected in the crash.
How much does it cost to reprogram or reset an airbag control module?
The cost to have your airbag control module reset or reprogrammed after a fender bender is usually around $50 to $100. This can usually be done at most auto repair shops and dealer service centers. Many warranty programs include it in the coverage.
Can an airbag module be repaired?
The only want to repair an airbag control module is to replace it. Though this usually doesn’t require replacing any airbag sensors. So, long as the sensors are still good.
How much does it cost to replace an airbag control module?
If the module itself is truly bad and cannot be simply reset or reprogrammed, the replacement part cost averages around $300 to $375. The labor cost to have a mechanic replace it will run you around $100 to $175 for a final repair bill of $400 to $550.
Can you drive without an airbag control module?
If you take the airbag control module out, or you have bad sensors that you don’t have replaced, you can still drive the car. Though you’ll get a variety of warning lights and warning messages. It might also affect your car insurance coverage if you or someone else is injured in a crash while driving without a properly functioning airbag control module or faulty airbag sensors.
Can I source a new airbag sensor from a junkyard?
These days scrap parts dealers are everywhere, offering all kinds of secondhand parts, including replacement airbag sensors. On the one hand, this is a great way to save money on the parts cost if you are dedicated to replacing your failing airbag sensors. On the other hand, you have no assurance that it will work correctly. Most automakers insist that you only use new parts from a certified dealer, and they might void any remaining coverage if you DIY install a replacement airbag sensor from a scrap dealer.
You also have to make sure that you are sourcing a replacement airbag sensor from an exactly matching make and model. Then make sure that they let you test it with a multimeter before any money changes hands.
The most obvious symptom of a bad or failing airbag sensor is the airbag light coming on and staying on when you start the car. The system automatically runs a diagnostic to determine that all the sensors and the airbag control module are working correctly. The system checks out normally if the airbag light flashes but stays off. If it stays on, you need to investigate further.
Usually, the cause of a bad airbag sensor can be traced back to a recent fender bender, a wiring issue, or perhaps water getting spilled on an interior door panel. If you can easily access the sensor, you can test it with a multimeter. Just make sure the car’s battery is disconnected first.
The parts cost tends to be the biggest factor in replacing a bad airbag sensor or a faulty airbag control module. You can expect to pay around $300 for the part alone, with only another $100 to $150 in labor costs to have a mechanic replace the bad airbag sensor.
Though if the problem can be traced back to a recent accident, your insurance might cover the replacement cost. Especially if you have full collision coverage, if your car is still under warranty, a dealership might be able to reset the airbag control module or handle the replacement of a bad airbag sensor as part of the service program.
Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.