iPhone 6 Plus cannot detect SIM card.
Upon inspection, this phone was repaired by some other repairer for touch IC issue.
Checked SIM card reader and found PP_LD5 SIM card power supply is grounded.
This point is linked to baseband PMU, baseband CPU and main PMU.
So I removed baseband cpu and PMU for initial inspection as I thought it must be baseband related.
It comes down to main PMU and it starts make sense.
It shorted because of previous touch IC repair heated the PMU and solder balls under PMU floated and contacted to ground.
This repair becomes more dangerous as main PMU is right behind CPU. Any extra heat can result CPU solder balls floate and just like the touch IC repair caused this PMU malfunction.
Well, informed client the risks and granted permission and proceed the repair.
Replaced main PMU and tested.
So when you are after some logicboard repairs, go to the experts, it doesn’t have to be me, but have to be someone with proven experience.