As it says HMC=0 you must delete this HMC connection first to get
anything displayed on the serial port after system has started:

http://publib.boulder.ibm.com/infoce...US/info/iphbp/
disconnecthmc.htm
(or just attach an HMC)

If this doesn't help try a factory reset:
http://publib.boulder.ibm.com/infoce...n_US/index.htm

Finally, call IBM :-)

Bye
Holger