SRS (Supplemental Restraint System) – Function, Components, Symptoms, and Possible DTCs

The SRS (Supplemental Restraint System) is a vehicle safety system designed to protect occupants during a collision. It works together with seat belts to reduce injuries by controlling airbags, seat belt pretensioners, and crash sensors.

What Does SRS Stand For?

SRS = Supplemental Restraint System

Main Components of the SRS System

• Airbag Control Module (ACM / SDM)
• Front Impact Sensors (FIS, LFIS, RFIS)
• Side Impact Sensors (LSIS, RSIS)
• Rear Impact Sensors
• Satellite Sensors
• Driver Airbag (DAB)
• Passenger Airbag (PAB)
• Side Airbags
• Curtain Airbags (CAB)
• Seat Belt Pretensioners
• Seat Belt Buckle Switches
• Occupant Classification System (OCS)
• Passenger Presence Sensor (PPS)
• Clock Spring
• Rollover Sensor

Main Functions

• Detects collisions.
• Deploys airbags when needed.
• Activates seat belt pretensioners.
• Monitors all safety system components.
• Stores diagnostic trouble codes (DTCs).

Simple System Diagram

 Impact Sensors
(FIS / LSIS / RSIS)
         │
         ▼
+----------------------+
| Airbag Control Module|
|     ACM / SDM        |
+----------------------+
         │
 ┌───────┼────────┐
 │       │        │
 ▼       ▼        ▼
Airbags Pretensioners
Clock Spring

Common Symptoms of an SRS Fault

• Airbag warning light ON.
• Stored SRS diagnostic trouble codes.
• Airbag system disabled.
• Seat belt pretensioner malfunction.
• Communication faults.

Possible Diagnostic Trouble Codes (DTCs)

• B0001–B0099 – Airbag and deployment loop faults
• B0010–B0015 – Driver airbag circuit faults
• B0020–B0028 – Passenger airbag circuit faults
• B0030–B0040 – Pretensioner and deployment loop faults
• B0050–B0065 – Seat sensors and buckle switch faults
• B0070–B0093 – Impact sensor faults
• B1000–B1003 – ACM internal faults
• U-codes – Communication network faults

Diagnosis Tips

• Use an SRS-compatible scan tool.
• Read and record all DTCs.
• Inspect connectors and wiring carefully.
• Check battery voltage and grounds.
• Follow manufacturer safety procedures before repairs.

Important Safety Warning

Always disconnect the battery and wait the manufacturer-specified time before working on SRS components. Airbags and pretensioners contain pyrotechnic devices that can deploy unexpectedly if handled incorrectly.

Frequently Asked Questions

Can I drive with the SRS warning light ON?

Yes, but airbags and seat belt pretensioners may not function properly in a collision.

What causes the SRS light to turn on?

Faulty sensors, wiring problems, low battery voltage, damaged clock springs, or control module faults are common causes.

Does SRS replace seat belts?

No. The Supplemental Restraint System is designed to work together with seat belts, not replace them.