Read the fine manual sir http://publib.boulder.ibm.com/systems/h ... 380581.pdf
Looking at that the STBY function shows it is sitting waiting to be started via the system processor. If there is a fault, it should be in the system processor logs. Might want to go diving through the system processor menus and see if you can dig that up. Generally, with the LED status codes if they come up and go away the test passes and it moves on, it's when they STOP on a code and display that you may have a fault.
E051 states it is "Reading processor VPD." If it STOPPED there it would indicate a problem but it is passing that test and moving to STBY mode waiting to start, as far as I can see. I have no idea what E054 is, it's not listed anywhere. Could you have read that off wrong?
It is then moving to STBY:
STBY - Service processor ready. System was shut down by the operating system and is still powered on. - This condition can be requested by a privileged system user with no faults. See service processor error log for possible operating system fault indications.
I think you just need to select ' System Power Control Menu > Power-On System' from the service processor console and it'll fire.