this is based on nfo by FatElvis. for comprehensive explanation chck his post at korgforums

you could use Midiox or Max to send these Sysex strings (f0...f7) to the PKP.
Sysex implementation chart: Padkontrol-Sysex-Imp (pdf, 40 KB)

a) Enter Native Mode [PDF section 2-2(16)]
f0 42 40 6e 08 00 00 01 F7

b) start lights [PDF section 2-2(19) + Table 4]
F0 42 40 6e 08 3f 0a 01 7f 7f 7f 7f 7f 03 38 38 38 F7

c) evoke KPK-buttons/pads to send sysex data [PDF section 2-2(17) + Table 3]
F0 42 40 6e 08 3f 2a 00 00 05 05 05 7f 7e 7f 7f 03 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 f7

d) make lights blink [PDF section 3-2(1)]
f0 42 40 6e 08 01 00 63 f7

e) control the LED [PDF section 3-2(3)]
f0 42 40 6e 08 22 04 01 50 57 4e f7