The airbag system is an important part of all modern vehicles.
Being an essential safety component of your vehicle, the advanced designs aim to improve the safety of the passengers in times of accidents. The airbag control unit is basically responsible for computing and processing the signals generated from the airbag sensors as to when and at what pressure the airbag should be inflated during the time of the collision or frontal impact.
The airbag control unit is the computer and brain of your vehicle’s airbag system, without which the sensors are also useless. Without a properly functioning airbag control unit, you run the risk of suffering serious damage in the event of an accident.
In some cases, the airbag light on your dashboard will illuminate even if there has been no accident. In such cases, it is usually due to a defective airbag control unit, or because an error has been generated internally in the control unit due to data corruption, damage or the effects of water. Such errors can be generated, or the airbag control unit can become bad, if water has entered the system or a short circuit has occurred.
Since the control unit is a typical electronic circuit with a board, ICs, and various chips, it is recommended that the airbag control unit is replaced with a new one when it is determined that the part is defective. Diagnosing and repairing the airbag control unit usually requires technical knowledge and there may be more problems than just one within the circuit. Therefore, for best performance and functionality, you should probably choose to replace it.
Airbag Control Unit Replacement Cost
The average replacement cost of the airbag control unit is between $3000 and $5000. However, the pricing usually varies depending on the car model and make.
The replacement process of the airbag control unit can be tricky due to its sensitivity. You must, therefore, take certain protective measures to avoid increasing the total cost of replacement. Basically, the cost of the airbag control unit depends on how many parts connected to the airbag control unit you also need to replace, because in certain cases you will need to replace other things as well. Apart from this, each vehicle can use a different type of airbag control unit, and the cost of the parts will also vary from vehicle to vehicle.
In addition, the labor costs for replacing the airbag control unit will be considerable if you do not do it yourself. An expert may need a few hours or even more to replace the control unit and repair everything correctly. This is something that can also increase labor costs. The airbag control unit can be brought in as a brand new unit, or there may be a used control unit for your car available on the market. If you decide to buy a new unit, you can easily expect to spend more than a thousand dollars on the parts, while the cost can be reduced by several hundred dollars if you buy a used one.
What is an Airbag Control Unit?
The airbag control unit can be considered as the most important part of the airbag system, or the brain of the airbag system that is installed in your car. It is the primary hub to which all sensors and other components of the airbag system are connected, including the belt tensioners on your seat belt, the collision and frontal impact sensors, the airbag itself and other components. It is like the airbag system’s motherboard and computational processor, which receives data from one end, processes and evaluates it, generates the commands, and then sends the signal commands to the respective components. The data and information about the collision are detected and recorded by the airbag sensors.
But what has to be done with this information is the decision that the airbag control unit has to make. The data from the sensors is transmitted to the airbag ECU or the control unit, which analyzes the readings and generates the most appropriate safety command in response. The airbag system’s ECU analyzes the readings of the impact speed and the impact area to decide whether or not the impact is hard enough to inflate the airbags.
In newer vehicles, the airbag control unit will also generate commands for preventive engine shutdown and interruption of the fuel supply. In some modern vehicles, the airbag control unit will also disconnect the battery for safety reasons in the event of an accident. Up to six sensors can be connected to the module of the airbag control unit in some vehicles, such as rotational speed sensors and tee acceleration sensors. The control unit can also intelligently receive and compare the signals and information received from the other sensors to assess when the airbag should be inflated. It can also send signals to switch on the interior lights and hazard warning lights.
The core functionality of the airbag control unit is to protect the occupants in rear and frontal collisions. Modern airbag control units use the SPEED platform approach as the latest safety concept. For mass production, computer-aided efficiency, improved safety and economic costs, the SPEED platform makes it a much more reliable and better option in the production of airbag control units.
Where is the Airbag Control Unit located?
The exact position of the airbag control unit can vary greatly for each vehicle depending on the type, design and preferences of the vehicle manufacturer. In most vehicles, the position of the airbag control unit is usually near the gear lever in the rear or front area. It may also be located under the handbrake lever. In some vehicle designs it may be located as a glove box in the proximal area of the gear lever or at the height of the handbrake. Sometimes it may also be located under the front passenger seat or in the footwell.
In other cases, the airbag control unit is located under the center console or on the floor under the radio. You may also find it under the carpet of the passenger seat or on the floor of the driver’s seat. Sometimes it can be difficult to see the exact location of the airbag control unit in your car, especially if you do not know what the airbag control unit in your car looks like. It is therefore recommended that you refer to the service manual provided by the vehicle manufacturer, which contains details of the location of the airbag control unit in your vehicle. Otherwise, you may need help from an expert or mechanic to locate the airbag control unit.
Replacing a Defective Airbag Control Unit
The replacement of a failed airbag control unit is a sensitive and risky business. If the instructions are not followed correctly, it can lead to life-threatening situations or inadvertently cause the airbag to inflate suddenly. Therefore, diagnosis or replacement can result in serious injury or even death, and it is extremely important to take the correct action when replacing the airbag control unit. The procedure will, of course, involve first removing the existing airbag control unit and installing the new control unit. Here are some steps you should follow when replacing a defective airbag sensor:
• Acquire all the tools you will need for the replacement.
• Keep the service manual guide with you
• Locate the airbag control unit with the help of the service manual.
• Make sure you don’t probe the sensor, seatbelt, or the control unit connectors
• Make sure that the vehicle is parked on a completely flat surface and not elevated or lifted with jacks.
• Do not probe the electrical connectors
• Do not disassemble or interfere with the pretensioners, retractors, safety inflators, or adaptive load limiters.
• Do not use electrical meters to diagnose from the SRS circuits
• Always turn off the ignition.
• Always remove the battery entirely and wait for a few minutes.
• Locate the SRS module.
• Unplug and disconnect the airbag control module.
• Install the airbag SRS components properly before replacing the airbag control unit.
• Make sure the clock spring, airbags, impact sensors, and the seat belts are properly installed.
• Remove all the bolts and ties that are mounting the control unit.
• Remove the old control unit module
• Match the old airbag control unit with the new one
• Install the new one in the right place and put the bolts on it.
• Replace and connect all the connections that you removed from it.
• After connecting everything back, finally, connect both the battery cables that you removed.
How to Diagnose a Defective or Failed Airbag Control Unit
As a rule, you should not carry out the diagnosis of an airbag control unit yourself by testing it with electrical probes or other means, unless you have sound technical knowledge, as this can be very dangerous. The very first indication you will see that something is wrong is the airbag light on the dashboard. In some vehicles, it may be illuminated in different ways; refer to your service manual to interpret the lights correctly. It can light up, flash once, twice, or three times, or be continuously lit. Each type of flashing corresponds to a signal for a specific problem. Other signals include the airbag not working at the time of an accident, i.e. at a time when you should definitely have things checked. Using the multimeter or the electronic tester can be dangerous for testing the airbag control unit. It is therefore recommended to avoid this. If you accidentally inflate the airbag, it can cost you three thousand dollars or more. Sometimes, when replacing the airbag control unit, other components need to be replaced as well.
Hi, I’m Magnus, the owner and the writer of Mechanic Base. I have been working with cars for 10 years, specialized in diagnostics and troubleshooting. I created this blog because I was tired of finding false information on the web while looking for repair information. I hope you enjoy my content!