ASF2 force off during boot (Latitude E7240 switches off 33 secs after pressing power on)

Hello all,

I own a Dell Latitude E7240 from 2014. Until recently the laptop worked fine with OS upgraded from the original Win8 to Win10. But now I frequently experience that the machine switches itself off while booting with a "ASF2 Force Off" event logged in BIOS events.

Searching for "ASF2 Force Off" on the internet and also in this forum, I found this error message beeing quite common for a variety of Dell laptops and other machines. Most often though, this appears to happen randomly while using the PC.

This case is different. The machine switches itself off in 80% - 90% of all attemps to boot. Then the timing is always as follows:

Fail:
00s Start button pressed
23s DELL logo displayed
28s If the m-sata drive is installed, Win10 starts to load (but will be interrupted). Otherwise the message about missing boot device is displayed.
33s Switches off

It usually takes 4 - 6 tries until booting succeeds. Then the timing is as follows:

Success:
00s Start button pressed
04s or 23s Dell Logo
Then normal operation (OS loads, etc. Most often, Windows then scans the HD because of the interrupted loading attemps from before.)

As soon as boot-up was once successfull, all works fine, including
- warm restarts
- the dell system test tools, both from bios and online from the dell website report no faults at all
- daylong PC stress test tools with high processor, graphics and HD load.

I already replaced the BIOS battery. I removed WIFI-adapter, half of the RAM, m-SATA drive, keyboard. Switched off any unnecessary onboard devices in BIOS (serial I/F, ...), loaded BIOS defaults, switched off C-states, ... Also renewed thermal paste for CPU / graphics chip. I use the latest available BIOS A29, but also tested with A15. Tested while powered by the original 65W AC adapter, battery only, or both.

All of the above does not change the behaviour, also the timing as described before remains exactly the same.

This clearly has nothing to do with Win10, wrong drivers, or anything of the kind, as the OS does not even need to be available. It also is the same when I test with some linux from a pen drive.


Any ideas on what else to try? Can anybody tell what happens during boot phase 33 seconds after pressing the power button (or 10 seconds after the DELL logo is displayed)?

The laptop is open at the moment from replacing the BIOS battery. I did not yet remove the motherboard and check the hidden side, where the first MosFets, inductors, etc. seem to be. But from the reachable side I can measure the 1.5V (for the CPU ?) beeing created and stable.

Thank you for any help

Chris