Use phonefix screwdrivers to remove the screws next to the iPhone lighting port, put the iPhone 6S on the Screen Separating Machine. After heating for a while, use LCD sucker and pry tools to remove the iPhone display assembly. Disconnect the iPhone battery, and then take out the iPhone 6S motherboard.
Continue to measure the iPhone motherboard, when measured 75_RFFE2_SDATA_BB, we found the Bus is short-circuited.
Log into the ZXW online dongle to check the iPhone 6S schematic diagram, this circuit is connected with many chips.
Put the iPhone motherboard on the PCB holder fixture, and then use hot air gun and tweezers to remove the related components one by one. After the UHBPA_RF high-frequency amplifier is removed, the resistance value of 75_RFFE2_SDATA_BB Bus get back to normal.
Clean the solder pad, and then install a new UHBPA_RF chip. Use Fluke digital multimeter to measure the iPhone motherboard again, all data measured are normal.
Hope these ways can solve your iPhone no SIM issue. If you have more effective methods, please comment below. Thanks for reading.