ABS light stays on & 4WD light flickers?????

Had new CV shafts put in and tech. says it's abs wheel sensors also 2 weeks later 4WD light started flickering but when I engage 4WD it goes out!!!But then goes back to flickering when in 2WD. Any help on either issue would help.Is there a code in the computer for ABS fault codes? Hate to spend $$$ on frt. wheel sensors and not fix prob.

There was a recall on the ABS module, have you already had that replaced?