There are two main ways to trigger the update from the SD card: Method 1: Force Upgrade (For bricked or stuck devices) Use this if the phone cannot boot to the home screen. : Turn off the device completely. Insert SD Card : Place the card containing the folder into the phone. Button Combination : Press and hold Volume Up + Volume Down + Power simultaneously. Automatic Start : The device should detect the UPDATE.APP file and begin the flashing process automatically. Wait 5-10 minutes for completion. Method 2: Software Upgrade (For working devices) Use this if you can still access the phone's settings. : Open the dialer and enter *#*#2846579#*#* Navigate Menu ProjectMenu Software Upgrade SDCard Upgrade
Safely eject the SD card and insert it into your Huawei CUN-L21. Step 3: Flash the Firmware (The Dload Method) huawei cun-l21 flash file sd card