The u2 in the query is a critical but often misunderstood term. It is shorthand for UART 2 or U2 Download Mode.

If you cannot root the N971N on U2:

On U2 firmware, the diagnostic port is locked. Use Z3X’s built-in Enable Diag function:

A technician searching for n971n u2 imei repair z3x is likely following a process like this:

When an SM-N971N loses its IMEI (usually due to a failed firmware update, corrupted EFS, or incorrect root attempt), the device shows:

The Z3X Samsung Tool (version 4.0 or higher) remains one of the most reliable professional boxes for Samsung Qualcomm repairs. For the n971n U2, the tool supports the following key features:

Samsung uses a binary/bit system for bootloader versions. The U2 (also written as B2 or U2) indicates the second revision of the bootloader for this specific model.