First check if the button is working.
I don't know about the 660cc. But the 1300cc has a vacuum system. It sometimes gets airlocked. I am able to fix it by fiddling with the vacuum tubes, removing and reinstalling and also trying to engage with the tubes removed etc.
If the vacuum is leaking then you'll have to find the leak.
Board kit which controls the 4x4 system can also malfunction. It can be replaced with a landcruiser kit if original suzuki isn't available.
