Well crap I knew it could be done but couldn't remember how....
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Saturday I had a height sensor go intermittent on me just as I was coming off the trail and about 140 miles from home. Of course the LR3 computers went to full panic mode and dumped me on the stops. (Why LR? Why?) With my Johnson rods, this then put the other sensors out of range as I could see on the in-dash display. I could clear the fault with the IId tool but it would immediately return. So I used the hi-lift to pick the truck up and get the sensors back into range, then cleared the fault, then the compressor would re-engage and put me back to normal height. Well, at least for a few miles until the faulty sensor would again freak the computer out and start dumping air. I though the IId tool would have a way around this but I was looking for a setting in the test/service menu to 'lock' the valves closed. Of course I didn't find that, although as explained a few posts back in this thread I could have done it by entering build mode...I just didn't remember that until I got back and re-read this thread.
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In the end I left the tool plugged in and just drove a few miles at a time until the red suspension fault light would come on, then I would immediately dive to the shoulder and quickly clear the fault with the tool before the truck had settled enough to put the other sensors out of range. Made for a looong drive home doing that every few miles but it did get me there.