Disconnect the charging cable and remove the display assembly. Run diode mode measurement of J2400. The measured value of Pin 5 is 436, which is normal. The measured value of Pin 2 is OL, which is abnormal. Normal value should be around 600. Judging by this, Pin 2 relevant circuit has been open-circuited.

Pin 2 of J2400 is the battery percentage detect signal of the phone, which connects to Pin 3 of Q2301 by way of FL2400. The rail extends to Pin F2 of U2300 by way of Pin 1 of Q2301 and then R2303. Also when we are measuring, we find that FL2400 is missing.