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thermalmonitord watchdog · missing sensor
Missing sensor(s): tg0b — Battery sensor TG0B (battery temperature)
The phone restarts about every 3 minutes with userspace watchdog timeout: no successful checkins from thermalmonitord and Missing sensor(s): tg0b.Multi-source
Where to look: Battery · Battery connector · Small parts beside the battery connector (data-line resistors/MOSFETs)
Bench checks
- Test with a known-good battery.
- Inspect the battery connector and the components next to it (easily knocked off during battery work).
- Diode-mode the battery data pins; OL = open line.
Board detail by model
Lines: I2C2_SMC_SCL_CONN, I2C2_SMC_SDA_CONN
Parts: R3201, R3202
- If a data pin reads OL, check R3201 and R3202.
Lines: PMU_TO_BATTERY_SWI
- Diode-mode the battery data pin PMU_TO_BATTERY_SWI.
- On 11 Pro/Pro Max the charge-port flex carries a second battery connection - swap it too (iFixit).
Lines: I2C2_SMC_SDA_1V8, I2C2_SMC_SCL_1V8
Parts: R2472, R2473, R2475
- Diode-mode I2C2_SMC_SDA_1V8 / I2C2_SMC_SCL_1V8 at the battery connector; OL = disconnected line.
- Check for missing resistors around the battery connector: R2472, R2473, R2475.
Lines: I2C3_SMC_TO_GG_SCL_CONN, I2C3_SMC_BI_GG_SDA_CONN
Parts: Q3200, Q3201
- Diode-mode the battery data pins.
- Check MOSFETs Q3200 and Q3201 for damage.
- Field case: a loose wireless-charging part caused TG0B/TG0V. Check it if the battery swap does not help.
Sources
- iFixit - iPhone Kernel Panics (accessed 2026-09-26)
- Repair Wiki - Troubleshoot and fix iPhone random restarts using panic logs (accessed 2026-09-26)
- iFixit Answers - iPhone XS TG0B = battery + parts beside battery connector (accessed 2026-09-26)
Hinglish me
Missing sensor tg0b: Battery sensor TG0B (battery temperature).
Kahan dekhein: Battery · Battery connector · Battery connector ke paas ke chhote parts (data-line resistors/MOSFETs)
Known-good battery se test karo.
Battery connector aur uske bagal ke components dekho (battery ke kaam me aasani se gir jaate hain).
Battery data pins diode-mode me naapo; OL = line open hai.