Some drivers report a soft brake pedal and suspect the cause is air in their ABS (after they've done a standard bleed on all calipers). For most ABS systems, I understand the ABS remains in a passive/off mode during normal driving and only activates when it senses an extreme imbalance in wheel speed during braking. In this case, if the ABS is a closed circuit during normal driving, how can air that somehow got into the ABS have any effect on normal braking and cause a soft brake pedal?