80 series center diff lock

I am looking at an 80 series Landcruiser 40th anniversary diesel manual. I could not find how to lock the centre diff for high range off road work. When it was put into low range the centre diff locked automatically and the ABS light came on. (Does this mean the ABS is turned off in low range)
I have owned a 94 petrol version which had an electronic switch on the dash which locked the center diff.
Did Toyota do something different for the newer versions or the diesel versions.