service ab system what does this mean. My breaks are working fine.

The ABS system is for the vehicle's anti-lock brake function. Something has malfunctioned in the system; may or may not be related to the bottoming out you experienced. A proper diagnostic test will lead a skilled technician to find out what area to focus on testing, likely a wheel sensor, tone ring or related wiring issue is present. The ABS system will typically not affect conventional braking operation, however, if you need to stop quickly, the function of the ABS system preventing wheel lock up and skidding may be compromised.

Recently had the same problem. I have an 07 lacrosse. It was the ABS wire harness which is attached to the wheel bearing. Most likely it is due to you bottoming out and in need of repair