When I first purchased the Jimny it had a problem where the 4wd switch did not appear to work. This switch is located on the Transfer Box and tells the Computer that 4 wheel drive has been selected which then vacuum locks the front wheel hubs.

The seller gave me a spare switch and as I intended off-roading immediatly I fitted the new switch, however it also failed to work. As a temporary work around I shorted out the wires on the switch connector. This told the Computer that the car was in 4wd drive and it locked the front hubs. Now I could select either 2wd or 4wd on the Transfer Box and it would work properly, however it did mean that I was driving around with the hubs locked (and so was burning more fuel) and the 4wd light was permanently on.

Looking at the workshop manual I could see that there was a small ball bearing associated with the switch (see below).

A quick check showed that this ball bearing was missing on my car. I got hold of an 8mm diameter ball bearing and popped it in and hey presto! - the switch now operates correctly. (note: a 10mm ball bearing also fits but it jams the switch in the "on" setting).