Unlocking a T-Moible Dash

i`ve got the the same truck,,pry up the corners of the dash grilles,carefully so not to crack them,usually the clips tend to break off,so grab some epoxy from hardware store first(gonna need it).Remove 4 7mm bolts and pull spkr out,,cut wires and strip,,,left side will have gray and tan,gray is positive,,right side will have light green and dark green,light green is positive(GM wiring is lights in the front,darks in the rear).Using connecters attach new spkr pigtails connect spkrs and re-install into dash. Using epoxy replace clips on grilles waiting for epoxy to set,,carefully replace grilles and your done. GOOD LUCK

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Hi there:
Check this on 1998 Chevrolet S10 Blazer Car Stereo Radio Wiring Diagram:

Car Radio Constant 12v+ Wire: Orange
Car Radio Switched 12v+ Wire: Dark Green
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: Violet/White
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Front Speakers Size: N/A
Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Rear Speakers Size: N/A
Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

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According to autozone online, there are two black wires for ground, a dark green to key power, orange to batt power, gray to dash lights, dark blue and dark green to steering wheel controls when equipped, a purple-while for light dimmer and gray to computer data link.
The dark green that has voltage powers the radio and the orange is for the station memory. The gray wire with power when the dash lights are on is for the radio light.

Call a dealer,to see if you really need a code. If you do,then a scanner will need to be used and a diagnostic fee charged.

BLACK - GROUND (-12v)
YELLOW - IGN (+12v WHEN CAR IS ON)
ORANGE - MEMORY (+ 12v ALWAYS ON)
GRAY - BACKLIGHT (ON WITH DASH LIGHTS)
BROWN - DIMMER
PINK - POWER ANTENNA (MAY NOT BE THERE)
LIGHT GREEN/DARK GREEN - RIGHT FRONT SPEAKER +/-
TAN/GRAY - LEFT FRONT SPEAKER +/-
DARK BLUE/LIGHT BLUE - RIGHT REAR SPEAKER +/-
BROWN/YELLOW - LEFT REAR SPEAKER +/-

Use a voltmeter or test light to tell the difference between the gray dash light wire and gray speaker wire, and yellow power wire and yellow speaker wire.

1987-89 Chevrolet Caprice Stereo Wiring Constant 12V+ Orange Switched 12V+ Yellow Ground Black Illumination Gray Dimmer Brown Antenna Trigger Pink Antenna Right Front Front Speakers 4" x 6" Dash Left Front (+) Tan Left Front (-) Gray Right Front (+) Light Green Right Front (-) Dark Green Rear Speakers 6" x 9" Rear Deck Left Rear (+) Brown Left Rear (-) Yellow Right Rear (+) Dark Blue Right Rear (-) Light Blue hope it helps

Constant 12V+ Orange Switched 12V+ Yellow Ground Black Illumination Gray Dimmer Brown Antenna Trigger Pink Antenna Right Front Front Speakers 4" x 6" Dash Left Front (+) Tan Left Front (-) Gray Right Front (+) Light Green Right Front (-) Dark Green Rear Speakers 6" x 9" Rear Deck Left Rear (+) Brown Left Rear (-) Yellow Right Rear (+) Dark Blue Right Rear (-) Light Blue

1998 Chevrolet Blazer S-Series Stereo Wiring Constant 12V+ Orange Switched 12V+ Yellow Ground Black Illumination Gray Dimmer Brown Antenna Right Front Front Speakers 6 1/2" Doors Left Front (+) Tan Left Front (-) Gray Right Front (+) Light Green Right Front (-) Dark Green Rear Speakers 6 1/2" Rear Doors Left Rear (+) Brown Left Rear (-) Yellow Right Rear (+) Dark Blue Right Rear (-) Light Blue

Constant 12V+ Orange Switched 12V+ Yellow Ground Black Illumination Gray Dimmer Brown Antenna Right Front Front Speakers 4" x 6" Dash Left Front (+) Tan Left Front (-) Gray Right Front (+) Light Green Right Front (-) Dark Green Rear Speakers 6 1/2" Front Doors Left Rear (+) Brown Left Rear (-) Yellow Right Rear (+) Dark Blue Right Rear (-) Light Blue

If you are a current T_Mobile customer, you can call them for the unlock code directly. If you have been with T-Mobile for at least 90 days, and have owned the Dash smartphone for at least 15 days, then you need to contact T-Mobile Customer Support by calling 1-877-453-1304 toll free. If you are outside of the country, the number is +15059983793. The representative will ask for your phone's IMEI#, which you already have, then they will process your request and email your unlock code to you within 48 hours.

I own a Dash myself, and I just had my phone unlocked last week.

Good luck!