The tool re-reads critical registers and attempts to mount the user area (typically via CMD17 / CMD18 read of sector 0). If successful, it may flash a known-good bootloader image.
CPU is still driving the bus. Fix: Find the CPU reset pin (often labeled RESET , NRST ) and ground it via a 100-ohm resistor. Alternatively, remove the main board battery and power only the eMMC via the tool. Efixer Tool Isp Emmc