In this page I will do my best to not only copy what others have done before me, but add to it a little..

first off, CricketCommunications, is a LeapWireless company, it is a bargain basement cellular prepaid service with NO FRILLS. including no analog mode, no data, no roaming, no sms, no support..

They have learned and updated with times, when i got my phone, there was no security, I could just enter nam programming mode, and change my alpha tag, and number and SIDS, emergency numbers.. .. ..Now everything requests a SPC code. Which im told is somehow phone specific, but ESN dirived..

Keypad Codes *3001#12345# will still get you into NAM Programming, on the newer phones, but to change anything aside from enabling Field test mode, you will need a SPC (Service Program Code) More on field test mode later, (if you enabled it, you will get some funny stuff on your screen when you reboot, use the arrow keys to move from screen 1 to 199 most are empty, but some have info, to view a primitive help hold down the * key for 5 seconds or so, and again to togle back, to make phone act like normal note the new menu item after "Lock Keypad" select Field Test 00)

Note, On the nokia 51xx phones actually locking the phone, (to prevent use,) can be bypassed if the nam access SPC has not been changed, see Despite being locked you can still enter *3001#12345# and get into the nam programming and read the lock code..

*#639# will let you program the network and phone number and such, but you need another SPC, default currently is 333333 (warning if you don't know these values, don't use this! your phone will loose service if you enter the wrong numbers!)

*#92772689# or *#warranty# will show the phones serial number & ESN &first programming date, (most of this can be had from the Nam programming menu)

*#170602112302# Shows SW version

*#837# or *#VER# or *#9999#Will show you the software version, and provider info,

*#7780 Resets factory defaults, (wont blank life timer, or phonebook)

Found on Gecko Beach Cellular Phone reset??
*#SLOT1# or *#SLOT2# reboots the phone!

Forcing other 800 and 1900 MHz CDMA networks from the 6185/8: If your service provider is using 1900 MHz CDMA (e.g., Bell Mobility, Clearnet PCS, Sprint PCS, Verizon, Wireless North, etc...), then you may be able to force your 6185/8 into 800 CDMA mode by entering *22800 or *22801 and hitting TALK. If you successfully contact a 800 CDMA network (e.g., Telus Mobility, MT&T Mobility, Verizon), you will hear a message from that network. Telus' message is: 'You've reached the customer service center at Telus Mobility...'. Hit 3 then 9 to listen to different rate plans from Telus which will give you a few minutes of looking through all the different test mode screens. Note that this procedure may take a few times to work -- you'll get assaulted with a tone if it doesn't. The Nokia 6185/8 allows you to track other CDMA providers' offset information and more.
This is how the *2280x searches for providers:
*22800 - 800 CDMA, Band A
*22801 - 800 CDMA, Band B (e.g., Telus in BC, Ameritech in Chicago)
*22802 - 1900 CDMA, Band A (e.g., Sprint PCS in San Franciso
*22803 - 1900 CDMA, Band B (e.g., Clearnet PCS, some Verizon)
*22804 - 1900 CDMA, Band C
*22805 - 1900 CDMA, Band D (e.g., Sprint PCS, Telus in BC) (cricket?)
*22806 - 1900 CDMA, Band E
*22807 - 1900 CDMA, Band F
Thanks to Peter Harren for providing information on the *2280x forcing
***BTW, cricket does not actually offer other bands, but it shows an interesting screen about unlocking service provide r .

once again the above info is from the great site Gecko Beach, look around there for stuff!

You can check your phone for a SP-lock or other network locks by following the procedure below.
Warning: if you enter any combination of the following strings more than 4 times then your phone may be rendered useless. Translation: this gives you one chance to enter each string one time only OR one string four times only. Enter these strings at your own risk.

Provider lock status: #pw+1234567890+1#
Network lock status: #pw+1234567890+2#
Provider? lock status: #pw+1234567890+3#
SIM card lock status: #pw+1234567890+4#

'P' is obtained by hitting the * key 3 times; 'W' by hitting the * key 4 times; and '+' by hitting the * key 2 times. The '1234567890' is the unlocking password string, so if you want to try one that you have obtained from an unlocking program then you would place it here instead of '1234567890'.

The above procedure will yield one of 2 results: SIM not restricted or Code error. A lock is indicated by Code error and your phone will reset.

That's all the keypads codes i have found that do stuff so-far..

  Now about the phone its self, To take it apart you need a T6 torq 
or  a very small flat-blade jewelers driver, remove the battery  then
remove the 4 black screw/s  now pop off the face of the phone, you will
find the white keypad/screen cover  comes off now,  now you can see the
key/screen board,  this board can be replaced with any of the boards from a 
 51xx series phone, Including LED mods boards (blue/red/white...) although
most of the led mod'd boards are in the UK.   The LCD display clips on on
the sides, and can be removed/replaced with any 51xx/61xx phone.
(replacing the led's in-fact even opening the phone may void your
warranty.. so just remember that).
     With the keypad board showing you can remove 2 silver head T6 screws
and you are down to the guts of the phone,  there is a plastic frame under
the screen board, and below that is the brain of the phone,  one piece
board that has the RX/TX ESN eeprom and power connectors, it is held in
place by one short t6 screw in the middle.. (btw, this board stores the
phone info including dialing directory, and more. it is often tossed by
repair shop's with data intact!)

Software

First off, most programs out there wont work with the 5170i, it is not because of anything cricket did to cripple the phone, its the fact while it takes the accessories and looks like a nokia 51xx its basically its own phone,

Parabon Fone Sync, for the 51xx/61xx works,
Logomanager can talk to the phone barely but you cant logomanage or edit anything.

Have yet to be compiled, but here is a directory of Field test screens, both with nokia help and with actrual values,, Field test Images