Airbag Sensor : Components, Working,Types, Symptoms, Test & Its Applications

Airbags are one of the essential security features, thus you must make sure that they are operational. Any issues with the highly responsive airbag sensors will turn on the airbag light. Airbags provide a cushioning system for the vehicle passengers by inflating immediately with air in an accident, so proper airbag usage is necessary for survival & injury safety in a crash. The airbag is an inflatable cushion arranged into a vehicle that guards occupants from hitting the interior or outside objects of the vehicle in a collision. The immediate crash starts, and sensors will measure collision severity. This article briefly explains an airbag sensor, its working, and its applications.

What is an Airbag Sensor?

The airbag sensor (crash sensor) is the input device of control signal within the SRS (supplemental restraint system) airbag system of the vehicle. Whenever the vehicle faces colliding, then this sensor will detect the vehicle collision’s intensity signal & input the signal into the airbag computer. So this computer decides whether to explode the inflatable element to inflate the airbag based on the sensor’s signal.

The function of the airbag sensor is to determine deceleration rates & provide precise data on the severity of a collision to check the airbags are deployed at the correct time & with the suitable force.

There are a minimum of two or more airbag sensors which change based on the manufacture of the vehicle. One set of these sensors is arranged right side of the front bumper whereas the other set is arranged in the engine for monitoring the deceleration rate. The third set is set approximately the dashboard as well as the passenger area, particularly seat belts. So the seat belt sensor checks the speed at which the vehicle passengers are thrown ahead because of the impact otherwise emergency stop.


This sensor is made of two main components; electrical and mechanical which are discussed below.
Electrical components have an electrical circuit & a switch connecting the sensor to the airbag control unit. Whenever the switch is pushed to complete the circuit, the airbag control unit enables the inflator to load the airbag.

Most mechanical components are designed with a ball as well as a tube. So a tiny magnet holds the ball on a single face of the tube. Whenever the collision occurs, the ball is removed from the magnet & rolls ahead. Upon attaining the end of the tube, then hit the electrical switch to finish the circuit.


Airbag Sensor Working Principle

Whenever a front crash occurs in a car then airbags are used. This crash impact is noticed by the airbag sensor. So an electronic signal from this sensor activates a chemical reaction to fill the airbag with secure nitrogen gas. These bags have vents; they immediately collapse after absorbing the energy of the occupant. They do not obstruct your movement and cannot suffocate you.

Location of Airbag Sensor

The airbag sensor or crash sensor connection diagram in a car is shown below. The crash sensor is installed in front of the car because the collisions mostly happen there. The sensor is located within the engine & one more security sensor of the same design is located in the passenger location of the car. So it is required to indicate which airbag sensor you are seeking for locating it exactly because these sensors are generally situated in different positions all over a vehicle. Before locating an airbag sensor, better to verify the user manual of the sensor is the best method.

Location of Airbag Sensor or Crash Sensor
Location of Airbag Sensor or Crash Sensor

These sensors are simply connected to the airbag module through a wiring harness. An airbag system’s two other main components are the diagnostic module & the indicator lamp. So the diagnostic module is used to perform a system test every time the car is turned ON, and the indicator lamp is temporarily mounted on the dashboard to light up.

Airbag Control Unit

The airbag control unit or electric crash unit is a module used to detect & also evaluate the harshness of an accident. After that, it triggers the suitable restraint systems. This unit is responsible for controlling the deployment of airbags, storage of crash data & also exchanging data with the engine of the car. Thus, if your airbag control unit is not good, then the airbags of the car may not react in case of an accident. Make sure if your airbag light in the car is on (or) it doesn’t arrange throughout an accident, then you have to get the SRS airbag unit reset. The airbag control unit main functions are; monitoring of car sensors: seatbelt data recording, car speed data storing & also recording other collision information.

Types of Airbag Sensors

There are two types of airbag sensors available; type sensor and roller-type sensor which are discussed below.

Mass-Type Sensor

The system of mass-type sensors includes two kinds of sensors. So the airbag impact sensor is placed at the front bumper of the vehicle. By positioning it at the front targets at the possible region a collision may take place.

When most vehicles at the front side have engines and it is also set within the engine. Once the crash crosses the grill toward the engine, the ACU (airbag control unit) can precisely decide it is a crash.
The second sensor in a type sensor system like an inertia sensor is set above the dashboard. So this safety airbag sensor above the dashboard checks the seat belts & transmits the data toward the airbag control unit.

Mass Type Airbag Sensor
Mass Type Airbag Sensor

The working principle of mass-type sensors is extremely simple. This sensor is set with a sensing ball within a tube. Whenever the impact occurs, this ball will be pushed forward to turn on a switch.

Roller-Type Sensor

Roller-type sensor is similar to the mass type but the type utilized within a car mainly depends on the company. This sensor has a weight that is connected to a coil spring component. Similar to the mass-type sensor, throughout impact by an oncoming car, the metal weight can be forced forward changing the tension above the coil spring to control the electrical circuit that turns off the contact of the sensor. It is significant to note that the effect & safety sensors should turn on and turn off simultaneously to allow for the use of the airbag.

Roller Type Sensor
Roller Type Sensor

Symptoms of Bad Airbag Sensor

The symptoms of a bad airbag sensor are discussed below.

  • The main sign of an airbag sensor malfunctioning is whenever your airbag light switches on without any reason. So it is a significant risk that can lead to failed airbags.
  • If the airbag light of the vehicle is flashing on your control panel, then your airbag has been stopped. The warning light sparks in a specific pattern to specify a troubleshooting code which can be obtained in the manual.
  • Airbag modules can degrade eventually. If this module is exposed to the moisture of light or flood injure, then this module will rust & the whole system will short circuit. If this airbag module is damaged, then you have to replace it immediately.
  • The clock springs of the Airbag wind around the steering wheel & connect to the electric wiring of the airbag system. So these springs also wear out eventually, which leads to your sensor specifying that a fault has occurred. This clock spring issue is sorted out by an auto repair specialist. If any damage within the spring is confirmed, then instant replacement is required.
  • If your vehicle’s headlights are left on during the night & you wake up to an exhausted car battery, chances have been exhausted also for a backup airbag battery. Recharging your car battery must assist with this difficulty—although if the lights of the airbag are still flashing; then there may be another failure somewhere within your control system.

How to Test Airbag Sensor?

An airbag is valueless if the airbag sensor doesn’t work properly. These sensors are used in many cars which help in resetting after an impact. But, not all kinds of vehicles are designed in this manner & the sensor may have to be manually reset or replaced after an impact. Testing the sensor is very important if an airbag is deployed.

Airbag sensors can be tested with an automotive diagnostic tool for recovering the real-time & error code data from the ACU. This is the safe way only to test this sensor. If there is any trouble code above the sensor, need to measure the wirings of the airbag sensor & airbag in the vehicle & make sure for any measuring results in your diagnostic tool.

Change the airbag sensor whenever the airbag control module specifies there is an issue although the connector & wiring are fine. So you should not interfere with these pieces because you want them to function in the incident of a disaster, although they are generally not extremely expensive.
The step-by-step procedure to test the airbag sensor is discussed below.

First Need to Determine the Issue

Once the engine is started, then the control modules mainly for the airbag will self-check the crash sensors automatically. So you will have to test the airbag sensor only if the warning light of the airbag lights up.

Scan Tool

A scan tool must be used on the airbag system. Ensure that you have your service manual out, thus you can recognize about trouble code. It is an excellent idea to write down this code for future reference.


Whenever you have a trouble code, then you will need to read up on your manual of the owner so that you will understand all of the situations for the possible difficulty.

Replace if Required

If the airbag sensor is bad, then the airbag won’t get the memo to blow up in the case of a disaster. To change the airbag sensor, place it near the face of the engine section. Unplug and unscrew the wiring and old sensor to install the new one.


The applications of airbag sensors include the following.

  • Airbag sensors are equipped in the airbags of cars to determine how harsh an impact was.
  • These are electro-mechanical-based chips, used for providing different kinds of inputs to the ACU (airbag control unit).
  • These are used in different kinds of airbags utilized within vehicles like the airbag in front of the driver, passenger, knee airbag, side airbag, etc.
  • The airbag sensor is responsible for noticing unexpected deceleration within a collision. So it transmits a signal to the ACU which utilizes the vehicle speed, seat belt yaw & ECU to decide if an airbag must deploy within a crash.
  • This is an input device for the control signal within the supplemental restraint system.
  • These sensors are broadly used in detecting collisions in different vehicles, particularly in the front.
  • This sensor is very significant to vehicle security.

Thus, this is an overview of airbag sensors, working, types, and applications. The automotive airbag sensor market global is expected to see significant development in the future. The growing focus on traveler safety & severe government regulations concerning vehicle security is driving the demand mainly for airbag sensors. In addition, the increasing number of accidents on roads & increasing advanced security adoption features within vehicles are fueling the development of the market. So the market growth can also be expected to profit from the incorporation of electronic sensors & higher technologies. Furthermore, the smart airbag systems development & the appearance of autonomous vehicles are estimated to boost the development of the market in the future. Here is a question for you, what is an airbag?