As we know, iPhone WIFI problem generally is caused by the iPhone WIFI Bluetooth IC, so now we need to disassemble the iPhone 8 Plus.
Use tweezers to remove the black sticker on the motherboard, and then use digital multimeter to measure the iPhone motherboard to check the iPhone WIFI working condition. After measurment, all data measured are normal, which means the iPhone WIFI circuits are normal.
Next, we need to measure the iPhone WIFI module IC working voltage. Connect the iPhone motherboard to a UNI-T DC power supply, trigger the iPhone motherboard, and then use digital multimeter to measure the motherboard.
Attach the iPhone motherboard to MJ A22+ PCB fixture, use hot air gun and BGA graver blade to remove the iPhone WIFI module IC, clean the solder pad.
Now use hot air gun and BGA graver blade to remove the iPhone Nand flash, and then clean the solder pad. Use JC PCIE NAND programmer to unbind the WIFI, and then reballing the iPhone Nand flash, install it back the iPhone motherboard.
Finally, assemble the iPhone 8 Plus, turn it on, now the iPhone WIFI icon displays normally, and it can be turned on properly, the iPhone 8P WIFI function is available.
Hope we can help you solve this annoying problem through the above hardware repair methods. If you have other better solutions, please leave a message in the comment.