I had my 2004 Lexus LS430 instrument cluster go out. Fully dead - no lights whatsoever. All the gauges were dead. The only lights working were the turn signals and check engine light. I tried everything - removed cluster and checked pin connections, rechecked battery connections, read and search for ground wire from battery. I also disconected the negative battery terminal multiple times and during one such time, the panel came back on momentarily. So, I knew it was not the panel and it was some loose connection somewhere.
While removing battery to search for ground cable, I noticed that the battery was more than 3 years old and figured that may also be a cause. Changed the battery and viola - my instrument cluster was back on!!
Not sure why I even suspected my battery - car started on first try always, radio,ac and everything else worked perfectly....just a lucky hunch I guess.
