Android fake overheating warning

I had the same problem. The phone shut down on itself a few minutes after every restart.

The timeframe was just long enough to install a hardware-checking-app. From the readings in the app I learned that an internal temperature sensor shows 90°C straigt. Even just after rebooting an login, despite I cooled it down to about 4°C the fidge before.

After removing the back cover, unscrewing all screws and finaly remoing the bezel, I managed to regain a true temperature reading by sligtly pushing an knocking the PCBs. Then I located the faulty sensor on the SUB-circuitboard next to the USB-connector by applying cold spray. Unfurtunately replacing the SUB-circuitboard has NOT fixed the issue.

To get the phone charged again I connected an USB-charger with was not plugged into the wall. Then i checked the temperature reading in the app and made it changing from fake 90° to real 27°-32°. Then I put down the Phone verry gently on something cushionlike to avoid disturbing the temperature mesaurement by vibrations. Then I and plugged the preconnected charger into the wall.

After reaching 85% I disconnected the USB-charger and the flexprint connector to the SUB-circuitboard. That disabeld the faulty temperature mesaurement, so I had not to expect the backup process beeing interupted by "safety shutdowns". Unconviniently also the USB is inoperable, when the flexprint is disconectet. So I culd not connect the Phone to my PC directly. Luckily the M32 features a µSD-card-socket.

I installed the app "SmartSwitch" and then inserted a card of 128Gb into the matching cutout of the SIM-tray. ThenI let "SmmartSwitch" saving everything to the µSD-card. It took over one hour (and a decent percentage of the battery charge) to copy everything, but wit the disconected sensor no inerruptions occured.

My M32 just developed the same issue out of the blue. Quoted £80 to replace sensor. I downloaded a temperature reading app and it shows the battery at 90*C constantly all while the device itself is cold to the touch, which keeps triggering shutdowns. While sitting it on an ice pack (tissue between to avoid moisture) I was able to transfer the files on my device to a microSD to save my photos and other data. I also checked temperature app while on the ice pack and the battery sensor showed 18*C. As soon as it comes off it jumps back up again. As the battery sensor is showing the faulty readings, it was recommended to replace the battery rather than sub board so going to try this first.