Malfunction Phenomenon
iPhone 7 Plus can not detect SIM card. And the Baseband information was normal with IMEI when we press *#06#.
Trouble Shooting
According to the malfunction phenomenon, we can try to check the SIM card reader firstly.
Use the multimeter to check the diode values on the SIM card reader J_SIM_RF, we found the value on pin 1 was 0, which means that pin 1 was shorted to the ground.
From the schematics, we could see that pin1 of J_SIM_RF was connected with BBPMU and Baseband CPU BB_RF via C5610_RF, C6900_RF, DZ6901_RF, so let’s continue to check the small components and chips.
Remove the 3 components one by one, but the line was still shorted. then try to remove the BBPMU and measure diode value again, the short was gone.
So the issue should come from BB_PMU, get it replaced, and test again, the function back to normal, the problem was resolved.
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