I own a 92 LS400, and I think I have the exact same problem. The guage cluster illuminates, tach works fine, temp and fuel guages work fine, just the speedometer and odometer have quit (as well as the trip A and B option). I bought another guage cluster and replaced it on my own only to have the exact same problem surface, so I'm certain its not the guage cluster. Friends have suggested that its probably the speed sensor (which makes sense since distance traveled and speed are related), and I downloaded a troubleshooting guide from TIS (Techical Information System) on how to see if it is indeed the speed sensor. I'm still dealing with finding a tutorial on how to replace it (or even get to it for that matter), but if I do come across a guide, I'll definitely let you know. Would love to hear back from you if you found a guide online on how to replace the speed sensor as well. Good luck and thanks!
