ABS Problems?

[(S.M.R) 101]

So yesterday I was scouting a proposed pipeline and I came up to a curve on this dirt road and there was still snow on it I was moving a little fast so I hit the brakes to slow down and the tires just locked up and I was sliding.. No ABS light or codes thrown but the ABS is not working you can feel nothing in the break pedal when you stop on a slipery surface just locks up the tires.... Any of you heard anything or had something happen like this to you? I know they were working just a few weeks ago we had a bad snow storm and I slid a few times while on the breaks and the ABS worked fine.