iPhone 8 — tg0b: Battery

What does this code mean?

Watchdog panic: thermalmonitord no longer receives data from the TG0B sensor, linked to the battery; with no response for ~3 minutes, iOS restarts the iPhone. No iPhone 8 / 8 Plus specific source found: rule extended from the general Repair Wiki guidance (“iPhone 12 series and older”) and from the iPhone 7 / X cases, which share the same battery architecture.

Which part to test first?

Check whether the battery percentage is displayed (stuck at 0–1% or “Service” = the iPhone can no longer read the battery), inspect the battery connector pins and the small components around it under the microscope (often torn off during disassembly), test with a known-good battery, then measure the battery data lines at the connector in diode mode (OL = open line).

The same code on other models

• iPhone SE (2nd generation)Battery
• iPhone 12 Pro MaxBattery
• iPhone 12 ProBattery
• iPhone 12 miniBattery
• iPhone 12Battery
• iPhone 11Battery
• iPhone XS MaxBattery
• iPhone XSBattery
• iPhone XRBattery
• iPhone 11 Pro MaxBattery or charging port flex
• iPhone 11 ProBattery or charging port flex
• iPhone 7 PlusBattery
• iPhone 7Battery
• iPhone 8 PlusBattery
• iPhone XBattery
• iPhone SE (1st generation)Battery data line: resistor near the battery connector

Field cases

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