iPhone 6 Plus Update System error 4014 repair

Machine model: iPhone 6 Plus
Fault phenomenon:Update System error 4014

iPhone 6 Plus Update System error 4014 maintenance Figure 1.

Maintenance process: the error 4014 is reported before Update System is issued.Recovery mode can recognize SN when it is expanded. This is generally caused by the problem of USB chip connecting to CPU.

Remove the machine and find that it is the main board of UMT. Remove the USB chip u1700 and measure the ground diode value from PAD to CPU, and find AP_TO_TRISTAR_ACC_UART6_TXD shows OverLoad and AP_BI_I2C0_SDA is also disconnected.

iPhone 6 Plus Update System error 4014 maintenance Figure 2.

iPhone 6 Plus Update System error 4014 maintenance Figure 3.

iPhone 6 Plus Update System error 4014 maintenance Figure 4.

iPhone 6 Plus Update System error 4014 maintenance Figure 5.

PCB circuit defect, find the external connection point or dig the light board to find the through-hole point of the line, AP_TO_TRISTAR_ACC_UART6_TXD is directly connected to the outside, without passing through other components, digging AP_TO_TRISTAR_ACC_UART6_During the TXD route, a via point was found beside the card slot, and Jump wire was excavated.