I have an issue where the core 7 of the CPU gets stuck at around 100% for long periods of time, for like an hour. The CPU temp rises to 50c and drains 20% of the battery. Restarting the phone immediately brings it back to idle. This happens a couple of times a month and the various system updates over the year haven’t fixed it.
I have tried to use the battery usage data and various battery monitoring apps to find out if it’s any of my apps doing it, but haven’t found any clear culprit. Have run the usual virus scans. I haven’t tried a factory reset but may have to do that.. Also haven’t tried a new sim card like fairphone support suggested (?) Is that even likely to help? Turning the data, location, bluetooth etc off doesn’t change anything either.
This is a frustrating issue that makes me consider getting some other phone if I can’t predict how much battery I will have left in the evening.
What is core 7, is it some specialized core? Are there any apps you suggest that could give me more insight into what the CPU is doing?
From the CPU info app and yeah you’re correct, it’s the 8th core apparently. It’s pretty easy to notice when the problem occures because the phone gets really hot.
Thanks Nordic for posting this, my FP5 does exactly the same thing intermittently. I think it started with the update to Android 15. Core 8 just gets pegged flat out, the phone heats up even while idle and runs the battery down. I’ve done a bit of investigating and discovered that if I force stop the Gmail app when this happens (closing it isn’t enough) core 8 returns to normal operation. The odd thing is that Gmail is not showing as having a heavy battery usage. Quite why Gmail should affect core 8 in this way I have no idea but it seems to fix it for me. I’d be interested to see if you could try force stopping Gmail (assuming you use this app) the next time core 8 in your phone goes crazy to see if this cures the problem for you too.
Thanks for giving it a try and sorry to hear it didn’t fix things. It’s a real puzzle, I’ve seen this overheating problem mentioned in other threads along with the excessive battery drain so we are not alone. I’d love to know what actually triggers this, I’ve found no rhyme or reason to it, it seems totally random.
It’s possible. Rather strange, varied and unexpected problems have in the past been solved with a new SIM. If your current physical SIM is over 5 years old I’d say it’s worth a try.
You might want to opt for an eSIM if you’re not already using one as a second SIM.
Would there be any particular circumstances, such as after having used the phone (maybe a single app) continuously for an unusually long time?
If you want to properly monitor cpu usage you should use the the android debug bridge (adb, included in the platform tools available here https://developer.android.com/tools/releases/platform-tools) and not some app. It allows you to open a direct shell on your phone and run various commands, such as the linux command top which allows you to precisely monitor resource usage. It will look like this (I opened the photos app and then took the screenshot, hence the high cpu usage in the corresponding column. The top command is also listed there for example, because it’s also a process currently running on the phone):
I have this exact problem in fairphone 6 but only after charging.
Scenarios:
Charge → Leave it. Phone will remain hot or warm, indicating that the CPU is doing constant work. Battery will discharge quickly, 20% or more during the night for example. When I wake up, the phone is still warm.
Charge → Reboot. Phone will remain cool, battery will last significantly more. After I charge it again to 100%, it will once again start draining faster.
I have managed to reproduce this behavior 4 times now. I will look into setting up adb and see which process is doing so much work constantly
I will try an E-SIM and see if it will help. I will report how it goes.
I haven’t been able to link it with any app or the way I use the phone. My normal heavy usage like watching videos doesn’t really increase the CPU temp above 35c and I get decent battery life. But this CPu issue raises the temp to 45+c, drains the battery and happens randomly even when the phone is in my pocket.
E-sim didn’t fix the issue. I feel my only option left is to try factory reset, if that doesn’t work I will have to try to claim extended warranty. Not fun to have to spend time trouble shooting this issue.
The “factory reset” is misnamed and can be misunderstood. It removes all apps and data but leaves the OS as it was from the last update. It is not a “clean install”, and certainly does not return the phone to the state in which it left the factory.
If your reply to Keneda’s question is “yes”, and you’re still seeing 100% cpu after the reset and before reinstalling your apps, then you can perform a clean install.
Note: only install the latest version.
If you install an older security patch level than the one already on the phone then you must not relock the bootloader because that would render the phone unusable and impossible for you to recover.
If you send in the phone for repair under guarantee (your other option) then I expect that it would, after expert examination, get a similar treatment (just my opinion).
Thanks for your reply. I will try the clean install and see if it helps. Maybe it will also fix the new issue with e-sim losing internet connection many times a minute.
I tried to clean install using Fastboot. OEM unlocking is turned on. The commands ADB devices and ADB reboot bootloader work fine. But fastboot flashing unlock does nothing. Any idea why? No prompt appears on the screen in fastboot mode.
Are you sure you’re in fastboot mode (and no longer in recovery mode)?
What happens if you type fastboot devices? It should give you a device code if fastboot is working.
