The airbag system is an important part of all modern vehicles. As an essential safety element of your vehicle, advanced designs aim to improve passenger safety in the event of an accident.
The airbag control unit is essentially responsible for calculating and processing the signals generated by the airbag sensors regarding the timing and pressure at which the airbag should be inflated during a 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 risk suffering serious damage in an accident.
In some cases, the airbag light on your dashboard will come on even in the absence of an accident. In such cases, this is usually due to a faulty airbag control unit or an internally generated error 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 faulty if water has entered the system or if a short circuit has occurred.
Since the control unit is a typical electronic circuit with a board, integrated circuits, and various chips, it is recommended to replace the airbag control unit with a new one when it is determined that the part is faulty. Diagnosing and repairing the airbag control unit usually requires technical knowledge and there may be more problems than just one in the circuit. Therefore, for better performance and functionality, you should probably choose to replace it.
Airbag Control Unit Replacement Cost
The average replacement cost for an airbag control unit is between $3000 and $5000. However, the price usually varies depending on the car model and brand.
The process of replacing the airbag control unit can be tricky due to its sensitivity. You must therefore take certain protective measures to avoid increasing the total replacement cost. Basically, the cost of the airbag control unit depends on the number of parts connected to the airbag control unit that you also need to replace, as in some cases you will also need to replace other items. Apart from that, each vehicle may use a different type of airbag control unit, and the cost of parts will also vary from vehicle to vehicle.
Furthermore, the labor cost to replace the airbag control unit will be significant 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 properly. 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 over a thousand dollars on 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 the most important part of the airbag system, or the brain of the airbag system installed in your car. It is the main hub to which all the sensors and other components of the airbag system are connected, including the seat belt pretensioners on your seat belt, the collision and frontal impact sensors, the airbag itself, and other components. It is like the motherboard and processing unit of the airbag system, which receives data from one end, processes and evaluates it, generates commands, and then sends signal commands to the respective components. Collision data and information are detected and recorded by the airbag sensors.
But what to do with this information is the decision that the airbag control unit must make. The sensor data is transmitted to the airbag ECU or control unit, which analyzes the readings and generates the most appropriate safety command in response. The airbag system ECU analyzes the impact speed and impact area readings to decide if 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 fuel supply interruption. 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 airbag control unit module in some vehicles, such as rotation speed sensors and 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 turn on the interior lights and hazard lights.
The basic functionality of the airbag control unit is to protect occupants in the event of a rear and frontal collision. Modern airbag control units use the SPEED platform as the latest safety concept. For mass production, computer-aided efficiency, enhanced safety, and economic costs, the SPEED platform makes it a much more reliable and better option in the production of airbag control units.
The exact position of the airbag control unit can vary considerably 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 at the rear or front. It may also be located under the handbrake lever. In some vehicle models, it may be placed as a glove box in the area proximate to the gear lever or at the height of the handbrake. Sometimes, it may also be located under the front passenger seat or in the floor.
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 passenger seat mat or on the driver’s seat floor. Sometimes it can be difficult to see the exact location of the airbag control unit in your car, especially if you don’t know what your car’s airbag control unit looks like. It is therefore recommended to refer to the maintenance manual provided by the vehicle manufacturer, which contains details on the location of the airbag control unit in your vehicle. Otherwise, you might need the help of an expert or a mechanic to locate the airbag control unit.
Replacing a Faulty Airbag Control Unit
Replacing a faulty airbag control unit is a sensitive and risky undertaking. If instructions are not followed correctly, it can lead to life-threatening situations or cause the airbag to deploy suddenly by accident. Therefore, diagnosis or replacement can result in serious injury or even death, and it is extremely important to take appropriate measures 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 to follow when replacing a faulty airbag sensor:
• Acquire all the tools you will need for the replacement.
• Keep the service manual guide with you
• Locate the airbag control unit using the maintenance manual.
• Make sure not to probe the sensor, seat belt, or control unit connectors
• Ensure the vehicle is parked on a completely flat surface and is 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 completely remove the battery and wait a few minutes.
• Locate the SRS module.
• Unplug and disconnect the airbag control module.
• Properly install the SRS airbag components before replacing the airbag control unit.
• Ensure the clock spring, airbags, impact sensors, and seat belts are properly installed.
• Remove all bolts and fasteners securing the control unit.
• Remove the old control unit module
• Pair the old airbag control unit with the new one
• Install the new one in the correct place and put the bolts on it.
• Replace and connect all the connections you removed from it.
• After reconnecting everything, finally connect the two battery cables you removed.
How to Diagnose a Faulty or Defective Airbag Control Unit
As a rule, you should not perform the diagnosis of an airbag control unit yourself by testing it with electrical probes or other means unless you have strong technical knowledge, as it 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 maintenance manual to correctly interpret the lights. It may light up, flash once, twice, or three times, or be continuously on. Each type of flash corresponds to a signal for a specific problem. Other signals include the airbag not deploying at the time of an accident, i.e., at a time when you should definitely have things checked. Using a multimeter or 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 could cost you three thousand dollars or more. Sometimes when replacing the airbag control unit, other components also need to be replaced.