This test result seems to say psu is working.
Subject pretty much says it all.  My G5 5000 gaming model will not boot, POST code 3 flashes orange, 5 flashes white indicating "Power Rail Failure: EC ran into power sequencing failure" I think this is probably a system board issue, but could it be a PSU issue?  I tried to reset the bios by removing bios battery, and also tested power-up with graphics card pulled with same results. Any ideas?  
G5 5000 Power Rail Failure -- is that system board or PSU?