iPhone 6 mobile 4G signal poor repair

Machine model: iPhone 6
Malfunction: mobile phone has poor 4G signal.

iPhone 6 mobile 4G signal poor repair figure 1.

Fault analysis: Mobile 4G has no signal. It is likely that there is a problem with the signal of 4G channel. This signal is high-frequency power amplifier and independent 4G signal ANT Switch, which may cause no signal of mobile 4G.
Maintenance process: Test that the mobile 2G and 3G signals are normal, that is, the 4G signals are absent, and the Unicom cards 2, 3 and 4G signals are normal. It seems that the fault should be in the related circuits of the mobile 4G signals.

First, replace the U_HBPAD high-frequency power amplifier. Measure that this PAD is normal to the ground diode value, and the replacement failure remains the same. Remove U_HBS_RF high-frequency ANT Switch, measure this pair of ground diode value, and find that the 2nd diode value-bit RFFE2_DATA signal is grounded OverLoad, which seems to be disconnected.

iPhone 6 mobile 4G signal poor repair figure 2.

iPhone 6 Mobile phone 4G signal difference maintenance Figure 3.

Looking at the schematic and location map, the RFFE2_DATA bus signal also goes to the nearby U_ASM_RF ANT Switch chip, which can come from the nearby Jump wire.