iPhone XR phone cannot activate troubleshooting

Machine model: iPhone XR
Malfunction: The mobile phone cannot be activated.

iPhone XR phone cannot activate troubleshooting Figure 1.

Maintenance process:mobileFailure to activate can generally be caused by several situations: first, the system version is low;Baseband is not recognized in the second type; The third CPU does not recognize the NFC chip; The fourth welding passed Nand SN and Bluetooth WiFi address did not match.
The machine has not been repaired. First, exclude the fourth type. In the activation interface, you can see that IMEI also excludes the second type no Baseband Version.

iPhone XR phone cannot activate troubleshooting Figure 2.

Now only the system version is low or there is something wrong with the NFC circuit.Update System reactivation failure is still the same. It seems that there is something wrong with NFC circuit. When the machine is disassembled, it is found that the motherboard NFC circuit has been repaired.

iPhone XR phone cannot activate troubleshooting Figure 3.

Suspected that it was not soldered properly, the chip was directly removed. By the way, by measuring PAD diode value, it was found that the REF diode value of NFC chip was abnormal, and the normal board diode value was OverLoad, but now there is diode value.