0x20000 — SMC: silent sensor
SMC “BSC failure” panic: the system management controller (built into the SoC) periodically waits for a response from each mandatory sensor; here, the silent element is on the logic board itself, most likely via the interposer that connects the two layers. With no response, it forces a restart, which repeats roughly every 3 minutes (≈180 s) as long as the sensor stays silent.
On iPhone 14 Plus, iPhone 14
Logic board: sandwich interposer (layer separation)
SMC “BSC failure” panic: the system management controller (built into the SoC) periodically waits for a response from each mandatory sensor; here, the silent element is on the logic board itself, most likely via the interposer that connects the two layers. With no response, it forces a restart, which repeats roughly every 3 minutes (≈180 s) as long as the sensor stays silent.
First check
Inspect the edges of the logic board for a gap between the layers; board repair (controlled heating, reballing).
On iPhone 14 Pro Max, iPhone 14 Pro
Gyroscope on the board (logic board sandwich separation)
SMC “BSC failure” panic: the system management controller (built into the SoC) periodically waits for a response from each mandatory sensor; here, the logic board gyroscope has stopped responding, typically after the two layers separate. With no response, it forces a restart, which repeats roughly every 3 minutes (≈180 s) as long as the sensor stays silent.
First check
No external part: check the gyroscope (U7300 according to Repair Wiki) and its pads, then the interposer; reball the sandwich or swap the lower board.