The location of the electronic airbag control unit is shown in the figure.
The ECU inflates the airbags based on a signal from the frontal impact sensor built into the airbags.
1. DC/DC converter: The power circuit DC/DC converter includes a boost and buck converter that supplies voltage to the four ignition circuits as well as an internal operating voltage. If the internal operating voltage falls below a certain limit, the system is reset.
2. Crash Sensor/Safety Sensor: The crash/safety sensor built into the airbag ignition circuit serves to activate the airbag circuits under all deployment conditions and maintain the ignition circuits in an unactivated state under normal driving conditions. The shock sensor is made in the form of a two-contact electromechanical switch, the contacts of which are closed under the action of negative acceleration exceeding a certain threshold value.
3. Backup power supply: The ECU has a backup power supply that ensures that the airbags are deployed within a short period of time in case of insufficient voltage in the on-board network or power failure in the event of a frontal impact.
4. Fault Detection: When the ignition is on, the ECU continuously monitors the system status and detects possible faults. Faults are displayed using the device «Hi-Scan» in the form of diagnostic trouble codes.
5. Malfunction indicator lamp (KLN): when a malfunction is detected, the computer warns the driver about it by turning on the warning lamp in the instrument cluster. KLN is the main means of alerting the driver about malfunctions of the airbag system. When the ignition is turned on for the first time, the warning lamp flashes six times, indicating a malfunction of the lamp itself and the PB ECU.
6. Recording fault codes: when a fault occurs in the system, the ECU records a diagnostic code in memory, which can only be deleted using the tool «Hi-Scan».
7. Using the data line connector located under the dashboard on the driver's side, the data stored in the memory of the computer is transmitted to an external device, in particular to the device «Hi-Scan».
8. When only the pretensioners are deployed.
9. Exit for unlocking door locks. This output is used to unlock the door locks upon impact. The signal from this output is 0-200 µA in off mode and 200 mA in on mode. When an unlock command is issued, the circuit breaker closes for 200 ms.