How to fix unknown Baseband version, null / invalid IMEI & SIM card not detected

Quite a number of MTK users have been having this issue on their MTK devices after flashing one ROM or another; something i call the 'Custom ROM fever'. This issue is mostly caused by wiping / corruption of the data partition. The Baseband and radio (for network signal) are controlled by the NVRAM (located in data/nvram/md/NVRAM/NVD_IMEI) and a file called MP0B_001.
Once this file is missing or the NVRAM partiton is corrupted, your phone's IMEI and radio functionality cease to exist. There are several methods to fix this:

Note: 

• Go to Settings > About and check Baseband. If it says Unknown then flash the Stock ROM / Firmware using Sp flash tool @ HERE to regain Baseband
•  For Samsung phones,  use octupus box

How to fix NULL IMEI on a Mediatek (MTK) Android phone

1. MP0B_001 Method [ROOT Required]

1. Search and Download ROM toolbox lite from Playstore 
2. Download IMEI.zip (to create a new IMEI file) then unzip the content of the folder (imei.exe) to a folder on your desktop 
3. In command prompt, navigate to the imei.exe containing folder you just created on your desktop
   * NOTE cd\ then enter (returns to root directory)
          
   
   Code:

   cd.. 
   
   Press Enter (goes up one directory)
          
   
   Code:

   cd foldername
   
   Press Enter (navigates to a folder called foldername)
4. A faster method is to open the imei.exe containing folder > Hold down Shift > Right-click on an empty space > Select "Open Command Window here"
5. When you're inside the imei folder in command prompt, type
   imei.exe <15digit_IMEI_1> <15digit_IMEI_2>
   eg
   
   
   Code:

   imei.exe 123456789111111 123456789111124  
6. Press Enter          
7. If both IMEIs you gave are of the correct format, a file named MP0B_001_NEW will be created. Rename it MP0B_001.
8. Now you can send it to the sd of your phone 
9. Install ROM toolbox lite then go to root explorer
10. In root explorer, delete the existing MP0B_001 file (located @ device/data/nvram/md/NVRAM/NVD_IMEI) and replace with the one you just created 
11. Long press the new MP0B_001, go to permissions and tick all 9 boxes at the top then select ok (don't tick special pernissions)
12. Restart your phone
13. Your SIMs should be detected, IMEI reflect and Baseband version change from unknown to what it should be.
    * Note that getting this done might not be this direct due to different scenarios but replacing the MP0B_001 file is the ultimate goal in order to fix the issue.

2. IMEI Replacement Method [ROOT Required]

This method involves the use of MTK droid tools and is only applicable when your SIM cards are detected but IMEI is invalid or null. To do this:

1. Download MTK droid tools
2. Download PdaNet
3. Enable USB debugging on the phone then connect it to the PC (don't enable mass storage)
4. Install PdaNet on the PC with the phone connected; you should get a message saying drivers installed successfully.
5. Extract then launch MTK droid tools on the PC (still with phone connected to PC)
6. MTK droid tools should detect and display your phones details
7. Click on IMEI/NVRAM
8. Supply the IMEI(s) then click replace
9. Restart your phone if it isn't automatically restarted
10. Your IMEI issue should have been resolved

3. NVRAM Restore Method [ROOT Required]

* Note that you need a working phone of the same model to backup NVRAM first 

1. Download MTK droid tools
2. Download PdaNet
3. Enable USB debugging on the GOOD phone then connect it to the PC (don't enable mass storage)
4. Install PdaNet on the PC with the phone connected; you should get a message saying drivers installed successfully.
5. Extract then launch MTK droid tools on the PC (still with phone connected to PC)
6. MTK droid tools should detect and display your phones details
7. Click IMEI / NVRAM
8. Click Backup
9. When backup is complete, open the MTK Folder > BackupNVRAM to confirm that backup was successful
10. Connect the phone with Basebrand / IMEI error to the PC still with MTK droid tools open
11. Still under IMEI / NVRAM, click Restore
12. Select the appropriate files from the windows that pop up
13. Reboot the phone once the procedure is complete

4. Engineering Mode Method [ROOT Not Required]

1. Download and Install Mobile Uncle  then grant superuser permission. You could also use MTK Engineering Mode
2. Select Engineer mode
3. Select Engineer mode (MTK)
4. Navigate to the Connectivity tab
5. Select CDS information
6. Select Radio Information
7. At Phone 1: Insert the command below then click Send at command
   
   
   Code:

   AT+EGMR=1,7,"IMEI1"
8. At Phone 2: Insert the command below then click Send at command
   
   
   Code:

   AT+EGMR=1,10,"IMEI2"
9. If you get an error like "This command is not allowed in user build" then leave a space between AT+ and EGMR as show below
   
   
   Code:

   AT+ EGMR=The rest of the code
10. Go back to Mobile uncle home screen
11. Click on Engineer Mode
12. Select Engineer mode (Android)
13. Select Phone information
14.  Click Turn on radio