Stuck in 4WD with light flashing after running with vacuum booster disconnected

I had to replace the front ABS sensors on my 56 plate VVTi Jimny. I drove it up onto ramps in 4WD low. I removed the brake booster hose to get better access to the plug on the ABS loom. Unfortunately the stud sheared off on the LHS sensor so without thinking I started the car backed off the ramps and drove it back up one ramp on full lock to get access with the drill to drill out the broken stud and re-tap the threads; it wasn't until I was back under the bonnet I realised why the engine didn't run very well.

When the job was finished I found that the transfer box is stuck in 4WD high, tested by both a wet grass test and jacking up and trying to manually turn a front wheel. I don't remember deselecting low range. The light is flashing but pressing the switches makes no difference. I use 4WD H and L fairly regularly so am familiar with how it should work. All wiring, fuses and vacuum lines appear to be as they should be. Any ideas where to look or what the problem could be. I'm thinking that running with the vacuum line to the brake booster has caused a condition that has upset something.

I have only had this happen when I managed to damage the wires on the transfer case. I switched the car off while in low range and when I started it again, it switched to 4H.

There is a good write up in the wiki about 4wd problems, I would have a look in there.

Apparently the transfer box and hubs can get out of sync, although there isn’t much information on it. I would switch the ignition off for an hour or so and then turn the ignition on, the 4wd controller should reset.

If that doesn’t work, you could try a battery disconnect.

When I snapped the ABS bolt on both front hubs, I just drilled it out from the outside of the hub, no need to get in from behind. The broken studs drilled easily and I didn’t need to re-tap, just clean the thread out with some spray.

So I am getting closer to finding the problem. Having exhausted all the obvious things like checking wiring and vacuum lines, fuses, disconnecting and reconnecting plugs on the transfer box and the same with the battery thinking it might reset everything no luck. Having studied the Wiki page I decided to to "fake" the signal from the vacuum line by bridging the white plug on the vacuum valve unit and on starting the 4WD light turned to solid green. I removed the bridging wire, plugged the plug back in and selected 2WD and the light went out after a couple of flashes suggesting that the vacuum signal was recognised I presume; I confirmed 2WD by reversing a gravel yard and giving it a boot full.

I then selected 4WD but got the flashing 4WD light despite 4WD being engaged tested on the gravel again. To get back to 2WD I had to bridge the white plug again and have now left it like that so the car is usable again. I suppose I need to check the hubs are disengaging when 2WD is selected next. I presume they are because the light extinguished when I selected 2WD with the white plug reconnected after "faking" the vacuum signal in 4WD. Assuming I am right I need to find why the vacuum signal works on disengage but not engage despite the hubs engaging.