Title: Kernel Panic - What & where is the TP3R sensor? (iPhone XS Max)

Question

iPhone XS Max

Released September 21, 2018. Models: A1921, A2101, A2102, and A2104 / Available as GSM or CDMA / eSIM or nano-SIM / 64, 256, or 512 GB / Silver, Gold, or Space Gray (Pronounced "iPhone 10 S Max.")

400 Questions View all | 42 Parts Shop

Mukhtar tasiu iro @mukhtartasiuiro

Rep: 13

1

Posted: Sep 26, 2026

Options

Title: Kernel Panic - What & where is the TP3R sensor? (iPhone XS Max)

Device: iPhone XS Max (iPhone11,6), iOS 18.7.10

Phone is repeatedly rebooting every ~3 minutes. Pulled the panic-full log from Analytics Data and it points to a missing sensor:

Missing sensor(s): TP3R

Full relevant panic string:

panic(cpu 2 caller 0xfffffff01c35fb44): userspace watchdog timeout: no successful checkins from thermalmonitord (2 induced crashes)

service returned not alive with context : is_alive_func returned unhealthy : current 7fffffffffdf, mask 37ffffffffdff, expected 37ffffffffdff. SD: 0 BC: 1 RC: 0 BS: 2, Missing sensor(s): TP3R

Build: iPhone OS 18.7.10 (22H374)

socId: 8020

Kernel: Darwin Kernel Version 24.6.0

I checked the iFixit Kernel Panics wiki page but TP3R isn't in the documented sensor table (only PRS0, Mic1/Mic2, TG0V/TG0B are listed). Given the "TP" naming pattern, I'm guessing it might be a temperature probe similar to TG0V/TG0B, possibly tied to the battery or charge port assembly, but I wanted to check with people who've seen this code before.

Has anyone run into TP3R specifically on an XS Max? What part/connector does it correspond to?

Thanks in advance.

Answer this question I have this problem too

Is this a good question?

Yes No

Score 1

1 Comment:

TP3R is a thermal sensor monitored by thermalmonitord. That exact ~3-minute reboot pattern plus Missing sensor(s): TP3R strongly points to a missing/disconnected sensor or its communication path, rather than a normal iOS issue.

I’d inspect the relevant flex/connectors and board circuitry rather than replacing parts blindly. You can also run the panic log through an iPhone panic log analysis to get the sensor fault and likely area summarized.

Sep 27, 2026 by ktel m Share

Add a comment

2 Answers

TP3R is a thermal sensor monitored by thermalmonitord. That exact ~3-minute reboot pattern plus Missing sensor(s): TP3R strongly points to a missing/disconnected sensor or its communication path, rather than a normal iOS issue.

I’d inspect the relevant flex/connectors and board circuitry rather than replacing parts blindly. You can also run the panic log through an iPhone panic log analysis to get the sensor fault and likely area summarized. — ktel m, Sep 27, 2026

ktel m @ktelm Rep: 1 3 · Answer 1 · 2026-10-04T09:47:12-07:00

ktel m @ktelm

Rep: 1

3

Posted: Oct 4, 2026

Options

That panic is pretty clear: thermalmonitord is timing out because it can’t see TP3R, which is why you’re getting the ~3-minute reboot cycle.

I’d treat TP3R as a hardware/sensor communication fault rather than an iOS problem. Check the relevant flexes and connectors around the battery/charging assembly and any recent repair work. An iPhone panic log analysis like Bim-Tech's can also help narrow down the missing sensor and likely repair area.

Was this answer helpful?

Yes No

Score 0

Add a comment

Jerry Wheeler @dadibrokeit Rep: 103.1k 162 90 158 · Answer 2 · 2026-10-04T11:20:43-07:00

Jerry Wheeler @dadibrokeit

Rep: 103.1k

162

90

158

Posted: Oct 4, 2026

Options

You are correct that we haven't run into the TP3R sensor before; it seems to be an extremely rare problem. The best clue I ran across was a FaceBook post where someone claimed that replacing the TIGRIS IC fixed the problem. That's definitely advanced board-level microsoldering repair work and not something us DIY-ers can fix ourselves. I'll let you see for yourself.

XS MAX RESTARTING ISSUES - Facebook

However, another advanced user had an iPhone 12 with water damage, and in this case their cause was a shorted signal line on the interposer between the two sandwich boards.

(6) Microtech - iPhone 12 restart every 3min Panic TP3R 🔥 • • The... - Facebook

Although we can't definitively say what the problem is on your phone, it seems to be fairly clear it's a motherboard issue that's going to require expert board level repair work to fix.

iPhone XS Max

Title: Kernel Panic - What & where is the TP3R sensor? (iPhone XS Max)

2 Answers

Add your answer