SRS Airbag Light On? Diagnose It with an Autel Scanner

What is SRS (Supplemental Restraint System)?

SRS (Supplemental Restraint System) is a passive safety system in modern vehicles used to protect occupants. It typically works in conjunction with airbags and seatbelt pretensioners.

The primary task of SRS is to respond quickly in the event of a collision, deploying airbags and tightening seatbelts to reduce the impact of occupants colliding with hard objects inside the vehicle, thus lowering the risk of serious injury or death.

The SRS control module may have different names in different manufacturers or vehicle models, but its core function remains the same: collecting collision/sensor data, determining whether to trigger protective devices, and controlling the operation of the airbags and pretensioners.

Composition of SRS System

Main Components and Working Principle of SRS

1. Sensors
   • Acceleration sensors, impact sensors, side impact sensors, occupant detection, etc.
   • These sensors continuously monitor vehicle acceleration, deceleration, and impact direction. Once the data exceeds a set threshold, a signal is sent to the control module.
2. Control Module (SRS/RCM)
   • Responsible for receiving and processing data from multiple sensors and running collision assessment algorithms.
   • Determines whether to trigger the airbags and records fault codes and historical collision data.
3. Inflators & Pretensioners
   • The airbag inflator inflates and deploys the airbag within milliseconds; the seatbelt pretensioner tightens the seatbelt before airbag deployment.
4. Other Components
   • Wiring and connectors, control relays, backup power (for some models), etc.

Working Principle of SRS System

What does the SRS Indicator Light on the Dashboard Indicating?

When the SRS indicator light (usually an airbag icon or the word "Airbag") remains on after ignition or while driving, it indicates that the system has detected a fault or failed its self-test.

Possible causes include: damaged sensors, open/short circuits in wiring, control module malfunction, loose airbag connectors, or failure to reset after a collision. Once the SRS fails, the system may not function properly in the next accident, so prompt diagnosis and repair are essential.

Common SRS Fault Codes

Note: Specific DTCs (Diagnostic Trouble Codes) may vary between manufacturers/models. The following are common example formats (using SRS codes starting with B as an example):

• B0020 / B0021: Left/Right Airbag Deployment Control Circuit Fault.
• B0100: Internal fault or power problem in the Airbag Control Module (ACM/RCM).
• B1234: Seatbelt Pretensioner Circuit Fault (Example only).
• U0121 / U0155: Network communication interruption (ABS/BCM and SRS communication failure).

Why is It Recommended to Use a Professional Scanner (Such as Autel)?

Using professional diagnostic tools allows for quick and reliable reading of SRS fault codes, viewing of real-time data streams, performance of special functions (such as module reset/matching), and clearing of fault codes after repair.

Compared to simply looking at the instrument lights, a scanner can tell you which specific sensor or circuit is causing the problem, saving troubleshooting time and avoiding misoperation.

Autel Scanner Allows Reading of SRS System

The Steps For Diagnosing SRS Using An Autel Scanner

The following uses common Autel diagnostic tools (such as MaxiSys, MK series, etc.) as examples to illustrate the standard diagnostic process:

1. Safety Preparation

• Bring the vehicle to a complete stop and engage the handbrake; ensure the ignition is set according to the manufacturer's requirements (some require ignition but not starting).
• Before performing any airbag hardware operations, disconnect the negative terminal of the battery and wait at least 5–15 minutes (recommendations vary depending on the vehicle model; please refer to your vehicle's repair manual) to prevent accidental airbag deployment.

2. Connecting the Equipment

• Connect the Autel scanner to the vehicle via the OBD-II interface and power it on.
• Open the Autel software and select the correct vehicle manufacturer, model, and year (to ensure protocol and function compatibility).

3. Entering the SRS/Airbag Menu

• In the diagnostic menu, select the "SRS," "Airbag," or "Restraint" system.
• Select "Read DTCs."

Diagnose SRS System With Autel Scanner

4. Read and Record the Fault Codes and Descriptions

• Record the code number and the description provided by Autel (e.g., B0028: Right Airbag Deployment Control Circuit).
• Use the "Live Data" function to view sensor values, such as accelerometer output, voltage, and ignition coil status (if applicable).

5. Troubleshooting Based on Information

• If the fault is identified as a circuit fault, check the corresponding sensor connectors, wiring, and grounding for proper function; check for airbag connector detachment or corrosion.
• If the fault is identified as a module fault, confirm that the module power supply and grounding are normal before deciding whether to replace the module and perform programming/matching.

6. Repair or Replace Components

Replace or repair sensors, wiring harnesses, or modules according to the fault location results. Advanced operations (such as replacing the SRS control module) usually require manufacturer programming and higher-level privileges; it is recommended that these be performed by a certified technician.

7. Clear Fault Codes and Verify

• After repair, use an Autel scanner to perform "Clear DTCs".
• Turn off and restart the engine, and confirm that the SRS indicator light on the instrument panel goes out after the self-test, and that the fault does not reappear after driving a certain distance (or several ignition cycles).

Clear SRS DTC With Autel Scanners

8. Perform Special Functions (If Supported)

Some Autel models support SRS module matching, post-collision reset, or calibration (dependent on vehicle). For these functions, please confirm that your Autel model supports the corresponding vehicle and function.

Post-Collision Repair and Precautions

• After airbag deployment, the following components must be replaced: airbag body, airbag wiring harness, SRS control module (depending on vehicle model), and any damaged sensors and seatbelt pretensioners.
• Always follow the manufacturer's repair manual: Repairing airbags and SRS systems involves safety risks; incorrect operation may lead to false triggering or malfunction.
• Pay attention to electrical safety: Disconnect the battery and wait the specified time before touching SRS components; perform a system self-test and diagnostic check after repair.
• Law and Insurance: Some countries/regions have regulations regarding safety system repairs after a collision, and insurance claims may require professional repair records.

When Should You Seek Professional Technician Assistance?

• You find that the SRS indicator light remains on or multiple unexplained fault codes appear.
• You are unsure which components need to be replaced or how to reset the control module after a collision.
• The SRS control module needs to be replaced and requires programming/vehicle network matching.
• You do not have the necessary tools or are unfamiliar with the operation of the airbag high-voltage ignition components.

The SRS Indicator Light Remains On.

Conclusions and Recommendations

The SRS (Safety Resistant System) is a critical system for ensuring the safety of vehicle occupants, and any related malfunctions deserve serious attention.

Using Autel scanners (such as the MaxiSys series, MK series, etc.) can significantly improve the efficiency of fault identification and troubleshooting: from reading DTCs and viewing real-time data to clearing fault codes and performing some advanced reset functions, Autel provides a diagnostic solution suitable for both home users and professional technicians.

However, when it comes to airbag installation/removal, control module replacement, or programming, it is still recommended to have these tasks performed by a qualified service station or ASE/manufacturer certified technician to ensure safety and compliance.