Time to time you do need to bleed your brakes. But did you know just like your engine oil you also need to replace your brake hydraulic fluid? If you have bled the brakes starting from the Right Rear, then the Left rear, right front and lastly the left front and you still have those squishy issues with your brakes? Then you need to remove the fluid from the reservoir and replace it with fresh fluid. Then proceed to bleed your right rear brake till you feel that you have brought the fresh fluid down to it. then top off the reservoir again and do the right rear side till you think fresh fluid has come from the equalization valve that is attached to your differential. Repeat for the right front then the left front. The reason for the pattern is that the right rear is the furthest from the reservoir. This has nothing to do with ABS itself but can affect how ABS performs during times of emergencies when it is active. Your ABS may or may not sense the issues I mentioned above but it is a cheep way to rule out the major things and to point you in the right direction. Note: During a four wheel brake replacement is a good time to bleed the brakes since the reservoir is full after pushing the fluid back to the reservoir when changing them. If your not changing pads/shoes then remember where your reservoir level was when you started and only put that much back in. This is to have space for the fluid to return to when pushing fluid back for the replacement. Also, remember that any brake fluid spilled needs to immediately cleaned up toughly or it WILL remove the paint on anything in or on your vehicle.