📌 What the Airbag Module (SRS / Airbag ECU) Is

• The airbag module is the central electronic control unit that manages the vehicle’s airbag system. It is also often called the SRS (Supplemental Restraint System) control module or airbag ECU.
• This unit constantly monitors impact sensors and other safety inputs. In the event of a collision that meets deployment criteria, it triggers the appropriate airbag inflators (driver, passenger, side, curtain airbags, etc.), helping protect occupants.  

📌 Key Functions of the Airbag Module

1. Sensors Monitoring
   It continuously reads data from crash/impact sensors, seat occupancy sensors, and other related safety sensors.  
2. Decision Making
   Based on sensor input, it determines if a crash event is severe enough to deploy airbags.
3. Airbag Deployment Control
   If a qualifying impact is detected, it sends electric signals to the airbag inflators so they deploy within milliseconds.
4. Crash Logging & Diagnostics
   The module usually stores crash data and fault codes which can be read with diagnostic tools (Toyota Techstream or OBD SRS scanners).

📌 Why It’s Important

• The airbag module is a critical safety component — if it’s faulty, the airbags may not deploy properly, or warning lights may stay on.
• After a collision where airbags deploy, this module often needs replacement because it stores crash event data and can disable itself for safety after activation.

📌 Replacement Notes

• Usually, replacement requires proper programming/resetting with a compatible Toyota diagnostic tool so the new module can communicate correctly with the vehicle’s systems.
• Simply plugging in a used module without resetting or clearing crash data may not resolve airbag warning lights.

🛠️ Typical Symptoms of a Faulty Airbag Module

• Airbag / SRS warning light stays illuminated on the dashboard.
• Fault codes related to airbag sensor/circuit errors when scanned.
• In some cases, airbags may not deploy when needed or deploy incorrectly.

If you want part numbers or compatibility info for the 30-series Alphard (AGH30/AYH30/GGH30), tell me your exact vehicle year and engine type and I can look up more specific part codes for you.