LG - Engineer menu

[NattyFido]

To access the Engineer Menu on LG phones. You can run various tests such as LCD test, Audio loopback test, Keypad test etc. You can check which version of software is on the phone and you can also do a Factory reset to put the phone in its original 'out of the box' state.

GM750 - 3845#*750#
GC900 & KM900 - 1809#*900#
KP500 & KP501 - 1809#*500#
U990, KU990 & KU990i - 3845#*990#
KC910 & KC910i - 3845#*910#

Older LG phones try 2945#*# or 338464#*#

[NattyFido]

More!

GT500 - 3845#*500#
GB220 - 1809#*220#

Basically try either 1809#*xxx# or 3845#*xxx# with the model number inplace of xxx.
There is one (can't remember which at the moment) where you have to press the call button after entering the code, but the others will go to the hidden menu as soon as you press the last # (without even displaying it sometimes)