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Seventh generation of iPad, released September 25, 2019, available in 32 or 128 GB models. Model Number A2197.

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Missing TG0B causes kernel panic, plus fluctuating battery level

The problem began 2-3 weeks ago while the device was charging.

Reboots are not spaced evenly at 180s apart, which probably indicates the sensor is responsive at times and not at others? At the beginning of the issue, I could sometimes use it for 5-10 minutes without rebooting, and sometimes less. Charge level fluctuates around 10-20% on each reboot and just randomly when unlocked. The reboots got more frequent and regular over time. Last night it seemed the iPad was charging very slow.

I took it for repair today,

They replaced the battery and the issue persists.

I've read TG0B is an NTC thermistor in the battery.... what could be the next steps? Any possible issues in the measurement circuitry?

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panic(cpu 0 caller 0xfffffff0243a0514): userspace watchdog timeout: no successful checkins from thermalmonitord
service returned not alive with context : is_alive_func returned unhealthy : current 1ffffffe, mask 1fffffff, expected 1fffffff. EC: 1 EH: 3758097110 3758097110 SD: 0 BC: 0 RC: -1 BS: 0, Missing sensor(s): TG0B
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This might be a late reply, but I had this error in my Wi-Fi iPad 7 as well after doing a logic board swap. I was able to use it for about 1-3 minutes after boot before it would kernel panic and restart. Turns out I forgot to fully screw in the battery, which likely caused a weak connection between the pins. If you could, try opening it up and just seeing if a battery screw is present. You might need to use a screw from a for parts iPad or take one from the upper bracket by the cameras.

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Mostly filling in details here without character limits, but I think @geirandersen is probably on the money here. The 180 second timing is textbook for this sort of issue. It's just the limit the iPad has set for the amount of time it will wait to get a reading. You can likely find this information if you need reading through the panic. But low quality batteries may also suffer the same issue as your original battery.

It's also possible the pin on the logic board carrying this signal was damaged during the repair. They can be quite fragile and are easy to damage based on the way the connection needs to be separated from board. The one indicated here is the one for the NTC line if that is the issue.

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Based on the schematic and boardview I have, the thermistor itself is on the battery's own board (If TG0B is actually the one on the BATT_NTC line). You can do some checking with a multimeter if you're so inclined to check for issues with this line, it can certainly be done. But it might be tricky to get a reading based on the location of the capacitor that is also on this line. It's under the shield that covers most of the logic board components. I will see how motivated I am to tear apart the iPad 7 I have to get a good picture and a known good reading once my coffee kicks in (It's not fully assembled, but the digitizer and LCD balance required to isolate the battery from the board is not my favorite).

It's might even be this isn't the issue at all. The fluctuating battery levels shouldn't be related to an NTC, that just monitors temperature. Battery levels are more likely related to the BATT_SWI line which gives "Gas Gauge" or charge level sort of data. But I'll elaborate more if necessary.

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Abraar Sameer, The first question is: Did the repair place use a good quality battery?

I’ve seen many, many users have issues with TG0B, and it has persisted through battery replacement. In all those cases though, it was the replacement battery that was the issue. I’ve used batteries from known good vendors (like iFixit, and a couple that’s here in Scandinavia) and the problem resolved on replacement.

I’m not saying it is 100% the cause for you, but it’s a start. I’ve even had a time when an iFixit replacement battery was at fault, but a second iFixit battery did the trick. Even iFixit is not immune to manufacturing trouble, but they are supreme in customer support and handling!

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Abraar Sameer will be eternally grateful.
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