See Power Off a PDomain.
See Remove a CMU for instructions.
Loosen captive screws at the four corners of the CMU.
Note - A LED might be lighted next to one of the two fault remind buttons to show you which of the two memory sections has a faulty DIMM. See DIMM Fault Remind Button .
Note - Energy cells on the board power the Fault Remind circuits for approximately 60 minutes after the CMU is removed from a power source. If the energy cells are depleted, the LEDs will not light. In that case, use the output of the show faulty command to determine the location of the faulty DIMM. See Locate a Faulty DIMM.