- The electronic control unit (ECU) acts like the brain of the air bag system: it receives signals from the various sensors (such as crash sensors) and decides if and when each air bag should deploy.
- The ECU is typically located in the middle of the vehicle or beneath the front seat, where it is well protected.
- In vehicles equipped with advanced air bag systems, the ECU can also receive input from additional sensors that detect occupant weight, seating position, seat belt use, and seat position to determine the force with which frontal air bags should deploy.
- The ECU also performs regular diagnostic checks of the air bag system. If the ECU identifies a problem, the air bag readiness (warning) light will illuminate on the instrument panel. When the air bag readiness light is illuminated, the air bag system might not perform properly in a crash.