As the title says, if you notice that your fans won’t return to whatever idle setting you have enabled (mine are set to 0%) but are stuck at 30% and that your GPU clock is stuck at 2Mz after you close the sim, despite nothing obvious using the GPU, there is a simple fix.
This only happens for me with MSFS and it was doing my head in, as only a PC restart would fix it. The solution is to make sure you don’t set power management mode to Performance in the NVCP, either global or specifically for MSFS. With that setting on normal the problem goes away.
This wasnt just for the 4090. I think the latest driver also effected the 3080 in my case. I had the same experience, roughly around the time after the driver update. DDU fixed it, but that reset the power management back to normal, like said above.