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Anthony Wilson

Member

Registered: 2020-10-15

Posts: 40

[SOLVED-ish] Thinkpad L15 temperature sensor failure

Yesterday I experienced a strange issue on my Lenovo L15 (AMD) laptop.
It was charging as normal (using the 60W charging adapter that came with the machine, over USB-C), and CPU usage was low, but the device became extremely hot (reportedly over 105°C) and the fan was not spinning.

EDIT:
Some time after I made this post, a UEFI update changed the thermal limits of the device and the CPU now aggressively throttles at 70°C. This isn't necessarily a good thing as it can kill performance, but it never gets anywhere near 100°C anymore.
As of 2025, the temperature sensor still occasionally malfunctions and the fan does not work on its own, so I either reboot (which usually resets and fixes the sensor) or control the fan manually.
END EDIT.

I checked the temperatures using the 'sensors' command, and this was the output (pay special attention to the temps near the end of the output)

amdgpu-pci-0600
Adapter: PCI adapter
vddgfx:        1.34 m
vddnb:       731.00 mV
edge:         +82.0 C
power1:       15.00 W

ucsi_source_psy_USBC000:002-isa-0000
Adapter: ISA adapter
in0:           5.00 V  (min =  +5.00 V, max = +20.00 V)
curr1:         3.00 A  (max =  +3.25 A)

thinkpad-isa-0000
Adapter: ISA adapter
fan1:           0 RPM
temp1:            N/A
temp2:            N/A
temp3:         +0.0 C
temp4:         +0.0 C
temp5:         +0.0 C
temp6:         +0.0 C
temp7:         +0.0 C
temp8:            N/A

nvme-pci-0100
Adapter: PCI adapter
Composite:    +54.9 C  (low  =  -5.2 C, high = +83.8 C)
                       (crit = +87.8 C)

iwlwifi_1-virtual-0
Adapter: Virtual device
temp1:        +66.0 C

ucsi_source_psy_USBC000:001-isa-0000
Adapter: ISA adapter
in0:           0.00 V  (min =  +0.00 V, max =  +0.00 V)
curr1:         0.00 A  (max =  +0.00 A)

zenpower-pci-00c3
Adapter: PCI adapter
Tdie:        +103.4 C  (high = +95.0 C)
Tctl:        +103.4 C

BAT0-acpi-0
Adapter: ACPI interface
in0:          11.96 V

As you can see, the "zenpower-pci-00c3" device showed temperatures over 100°C.

Keep in mind that the laptop could have been this hot for up to 5 minutes before I realised, and the fan never came on.

For reference, here is a normal output from the 'sensors' command (it's not plugged in though, so not quite the same)

amdgpu-pci-0600
Adapter: PCI adapter
vddgfx:      756.00 mV
vddnb:       593.00 mV
edge:         +29.0 C
power1:        6.00 W

ucsi_source_psy_USBC000:002-isa-0000
Adapter: ISA adapter
in0:           0.00 V  (min =  +0.00 V, max =  +0.00 V)
curr1:         0.00 A  (max =  +0.00 A)

thinkpad-isa-0000
Adapter: ISA adapter
fan1:           0 RPM
temp1:        +29.0 C
temp2:            N/A
temp3:         +0.0 C
temp4:         +0.0 C
temp5:         +0.0 C
temp6:         +0.0 C
temp7:         +0.0 C
temp8:            N/A

nvme-pci-0100
Adapter: PCI adapter
Composite:    +28.9 C  (low  =  -5.2 C, high = +83.8 C)
                       (crit = +87.8 C)

iwlwifi_1-virtual-0
Adapter: Virtual device
temp1:        +28.0 C

ucsi_source_psy_USBC000:001-isa-0000
Adapter: ISA adapter
in0:           0.00 V  (min =  +0.00 V, max =  +0.00 V)
curr1:         0.00 A  (max =  +0.00 A)

zenpower-pci-00c3
Adapter: PCI adapter
Tdie:         +29.8 C  (high = +95.0 C)
Tctl:         +29.8 C

BAT0-acpi-0
Adapter: ACPI interface
in0:          11.36 V

As you can see, when the laptop got extremely hot the 'thinkpad-isa-0000' device had a missing temperature, when normally that first temp would be correct.
I assume this is why the fan never came on, but why would the sensors malfunction like that?
Could this continue happening in the future?
Why didn't the laptop turn itself off or at least stop taking power from AC when any of the sensors reported those high temps?

Something that I have noticed is that the values in the device file /proc/acpi/ibm/thermal are a little strange.
Normally, it looks something like this:

temperatures:	32 -128 0 0 0 0 0 -128

But yesterday when the laptop got very hot, the contents of this file showed this:

temperatures:	-128 -128 0 0 0 0 0 -128

As soon as I realised, I unplugged the charger, and the temperature started going down, but I had to leave the laptop on because of that call.

I hope someone can give me some info about the devices shown by the 'sensors' command, and whether or not anything will be damaged from those temperatures.
I'm also hoping someone might have some information about the values in /proc/acpi/ibm/thermal - why does only the first sensor show a temperature? Is this a firmware problem?
Why would that sensor just stop working?

This is not a kernel 5.11 bug. This happened while I was using kernel 5.10.16 (I have since updated to 5.11)

Last edited by Anthony Wilson (2025-01-21 20:52:31)

raindog1975

Member

From: Romania

Registered: 2017-04-04

Posts: 24

Re: [SOLVED-ish] Thinkpad L15 temperature sensor failure

The fan should be controlled by the BIOS by default unless something in the OS is inhibiting that behavior.

Anthony Wilson

Member

Registered: 2020-10-15

Posts: 40

Re: [SOLVED-ish] Thinkpad L15 temperature sensor failure

Small update: that sensor randomly failed again. This time I powered on the laptop, set the charging thresholds, and turned the charger on (that's it).
I only realised after that that the first value in /proc/acpi/ibm/thermal shows -128 (I'm quite sure it was correct until I turned on the power, but I can't say for sure).

I rebooted, and that fixed the problem - as expected.
I also had a look at the two journals, but couldn't fine anything that would suggest a sensor failure of any kind. Other than some different systemd start orders, everything was exactly the same between them.

Obviously there's something wrong here with the sensor (likely why the fan failed), which seems to happen only rarely.
If this was a BIOS issue I'd expect it to be more widely reported by now, unless it only affects Linux only some of the time, and I was just unlucky that the laptop reached those very high temperatures.

If anyone could inform me about the sensors, or about the health of my laptop now, that'd be great. This isn't a huge issue, but I'd like to know if I should contact Lenovo about this, or just leave it and keep a close eye on my temps.