Sim-Unlocker Pro

Sim-Unlocker Pro — Dedicated SIM Network Unlock Tool

5 min read

What is Sim-Unlocker Pro?

Sim-Unlocker Pro is a dedicated SIM network unlock tool focused on removing carrier locks from phones so they can be used with any SIM card worldwide. Unlike multi-function GSM tools that handle dozens of operations, Sim-Unlocker Pro specializes in one thing: removing carrier/network SIM locks.

How SIM Network Locking Works

When a carrier sells a subsidized phone, they program a network lock into the device that restricts it to only accept SIM cards from their network. The lock is stored in the phone's security partition and checks the SIM card's MCC/MNC (Mobile Country Code/Mobile Network Code) during startup. If the SIM doesn't match the authorized carrier, the phone displays "SIM not supported", "Network locked", or "Enter SIM unlock PIN".

Unlock Methods

Code-based unlock: Server calculates the correct 8-16 digit unlock code based on the phone's IMEI and carrier algorithm. Code is entered directly into the phone's unlock prompt
Direct USB unlock: For devices where code-based unlock is not available, the tool connects via USB and patches the network lock data directly
Server unlock: Some devices (newer Samsung, newer iPhones) require a server-side unlock that communicates with Apple/Samsung activation servers to whitelist the IMEI

Supported Brands

Samsung — Galaxy all series, all carriers (T-Mobile, AT&T, Verizon, Sprint, Cricket, etc.)
Huawei/Honor — unlock codes via algorithm
LG — direct unlock and code-based
Motorola, ZTE, Alcatel, Nokia, HTC, Sony — code-based unlock

Credit-based per-device model — one unlock uses one credit allocation.

How to Use Sim-Unlocker Pro: Step-by-Step

Purchase Sim-Unlocker Pro credits from Code-GSM
Download the software and install on Windows PC
Log in with your credentials
Connect the carrier-locked phone via USB
Click "Read Phone" — the tool reads IMEI, model, and current carrier lock status
Select "Unlock" — the tool applies the appropriate unlock method:
- Direct NV patching (for supported models)
- Server code calculation (for code-based unlocks)
- Firmware patching (for bootloader-level locks)
Phone reboots — insert a different carrier SIM to verify unlock

Tips

Check lock type first: NCK (Network Control Key) is the standard SIM lock code
Some phones need a defreeze code before the NCK code will work
After unlock, verify by inserting a SIM from a different carrier and checking for signal

Browse Sim-Unlocker Pro at Code-GSM

Device Connection Modes — How to Enter Them

Most phone servicing tools require the phone to be in a specific low-level mode before connecting. Here is how to enter each mode:

Mode	Chipset	How to Enter	Windows Device Manager shows
BROM / PreLoader	MediaTek (MTK)	Power OFF phone → press and hold Vol+ OR Vol- (varies by model) → plug in USB cable. Alternatively use test point to short BROM pads	"MediaTek PreLoader USB VCOM" or "MT65xx" or "MediaTek USB Port"
EDL (Emergency Download)	Qualcomm (QC)	Use ADB: `adb reboot edl` OR short the EDL test point on the PCB while plugging USB. Some devices: hold Vol Up + Vol Down while connecting USB	"Qualcomm HS-USB QDLoader 9008" or "QHSUSB__BULK"
Download Mode	Samsung	Power OFF → hold Vol Down → connect USB cable (newer Samsung). Older models: hold Vol Down + Home + Power simultaneously	COM port appears in Odin (yellow box)
SPD Download	Unisoc/Spreadtrum	Power OFF → hold Vol Down → connect USB cable	"SPD Interface" or "SPRD U2S Diag" in Device Manager
Fastboot Mode	All brands	Power OFF → hold Vol Down while connecting USB OR via ADB: `adb reboot bootloader`	"Android Bootloader Interface" or "Android" in Fastboot
ADB Mode	All brands	Enable USB Debugging in Developer Options (Settings → About → tap Build Number 7× → Developer Options → USB Debugging). Connect USB → authorize PC on phone	"ADB Interface" or device listed under Android devices

Understanding NCK, SPCK, and Freeze Codes

Some phones require multiple codes to complete the unlock. Sim-Unlocker Pro handles all code types:

Code Type	Purpose
NCK (Network Control Key)	Main SIM network unlock code — removes the carrier's SIM lock
SPCK (Service Provider Control Key)	Unlocks from a group of carriers under the same service provider
NSCK (Network Subset Control Key)	Unlocks a network subset (rarely needed)
MCK (Modem Control Key / Defreeze)	Used when too many wrong NCK attempts have "frozen" the unlock counter. Must be entered BEFORE the NCK

Sim-Unlocker Pro automatically calculates and applies all required codes in the correct order.

Troubleshooting Sim-Unlocker Pro

Problem	Solution
Device reads as "already unlocked"	Insert a different carrier SIM to verify. If it works, the phone is indeed unlocked. If not, retry detection after reboot
"Phone counter is 0" / exhausted	The unlock attempt counter has been used up from previous failed codes. Contact code-gsm.com — this requires a specialized defreeze/counter reset service
Unlock code rejected by the phone prompt	Ensure the code was entered for the exact IMEI/carrier. Try requesting a new code from code-gsm.com support
Tool detected wrong carrier for device	Manually select the carrier from the tool's dropdown. The auto-detection reads the current inserted SIM, not the lock carrier

Frequently Asked Questions

Q: How do I know the unlock worked?
A: Insert a SIM from a different carrier — if you see no lock prompt and get normal signal bars, the unlock is complete.

Q: Can a phone be "re-locked" after unlock?
A: Phones unlocked via direct USB NV patching cannot be re-locked. Manufacturer server-based unlocks (Apple, Samsung official) are also permanent and cannot be reversed by carriers.

Q: Can Sim-Unlocker Pro recover a phone that hit maximum attempt lock?
A: On most models yes — via MCK (defreeze) code. The MCK resets the attempt counter, allowing the NCK to be entered. Contact code-gsm.com with your IMEI for a defreeze code.

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