I have an '03 IS300 and the cluster is giving me a weird problem. It was intermittent before but now it seems to be a hard fault. The tachometer is reading zero, the brake light warning is on as is the fuel pressure light, and I also have nothing registering on the fuel consumption guage. It seems to have no effect on the car, traction control, cruise, speedo, all seem to be alright. I went through the wiring diagrams and could not find anything common with all 4 of these items. Please help if anyone knows! Thank you!

Those are a strange combo of issues. At this point I would have more questions than answers though. Like, your IS300 has a fuel pressure light? How did you get one of those?
So when you say your tach read zero, you mean it's not working at all? That is a seperate issue. You have a speed sensor off the Transmission for that. The brake light warning system is telling you that one of your lights are out. Have you gone around and checked to make sure all the lights are working properly? That warning doesn't have any effect on the ECU safety protocol, so traction control and cruise would all not be effected.

Sorry, I meant oil pressure, poor proof read on my part. All of these problems are intermittent but they all happen at the same time, none of them occur individually. All of the lights work, and the oil level is fine.

I think you may have a tach issue that is creating the other light sensor issues. When the tach fails, ie: shorting out, going bad, whatever, you may be getting a voltage drain or flux that may be effecting some of the circuits next to it. which could be the two other issues that appear at the same time. There is also a wire harness that runs along the trunk that the factory was known to have wrapped way to tight and I have seen some strange issue spawn from that. You might want to check that out as well. But in any case, I think this isn't something that we would be able to diagnose and fix over the forums. You should probably take it in and show them what is going on. It might be worth tracking down and just getting it fixed before it starts to decay into other issues as well.