FO4 ctd direct after launching in MO2

[schwarzbrand]

I reinstalled FO4 with steam. Downgraded it to 10.163 via downloading archives and installed some mods and played some test runs.

A few days later the game won't start anymore. MO2 wants to launch the game, the screen goes black for a second or two and then jumps back to MO2. No crash log. MO2 log waits for fallout4.exe, then goes back to desktop.

No missing master, no change in the load order, no limit problems and F4SE installed correctly.

Even launching via steam is not possible anymore.

I deleted the steam game folder and downloaded everthing again. The game starts as the newest AE version. But after downgrade and using MO2 the game won't start anymore.

 

MO2 log:

[2026-08-06 19:46:54.653 D] Updating VFS mappings...
[2026-08-06 19:46:55.382 D] VFS mappings updated, linked 623 dirs and 5 files in 736ms
[2026-08-06 19:46:55.386 D] checking steam
[2026-08-06 19:46:55.386 D] managed game is located at 'C:/STEAM/steamapps/common/Fallout 4' and file 'C:/STEAM/steamapps/common/Fallout 4/steam_api64.dll' exists
[2026-08-06 19:46:55.390 D] 'steam.exe' is running, accessible=yes
[2026-08-06 19:46:55.390 D] spawning binary:
[2026-08-06 19:46:55.390 D]  . exe: 'C:/STEAM/steamapps/common/Fallout 4/f4se_loader.exe'
[2026-08-06 19:46:55.390 D]  . args: '-forcesteamloader'
[2026-08-06 19:46:55.390 D]  . cwd: 'C:/STEAM/steamapps/common/Fallout 4'
[2026-08-06 19:46:55.390 D]  . steam id: ''
[2026-08-06 19:46:55.390 D]  . hooked: true
[2026-08-06 19:46:55.390 D]  . stdout: no
[2026-08-06 19:46:55.390 D]  . stderr: no
[2026-08-06 19:46:55.390 D]  . real cmd: '"C:\STEAM\steamapps\common\Fallout 4\f4se_loader.exe" -forcesteamloader'
[2026-08-06 19:46:55.400 D] process tree:
[2026-08-06 19:46:55.400 D]     f4se_loader.exe, pid=11316, ppid=9028
[2026-08-06 19:46:55.400 D] waiting for completion on f4se_loader.exe (11316), strong interest
[2026-08-06 19:46:55.479 D] process 11316 completed
[2026-08-06 19:46:55.483 D] process tree:
[2026-08-06 19:46:55.483 D]     Fallout4.exe, pid=11080, ppid=11316
[2026-08-06 19:46:55.483 D] waiting for completion on Fallout4.exe (11080), strong interest
[2026-08-06 19:47:02.118 D] process 11080 completed
[2026-08-06 19:47:02.118 D] nothing to wait for
[2026-08-06 19:47:02.119 D] process runner: refreshing because the process completed
[2026-08-06 19:47:02.120 D] refreshing structure
[2026-08-06 19:47:02.122 D] refresher: using 10 threads
[2026-08-06 19:47:02.307 D] refresher saw 71150 files
[2026-08-06 19:47:02.307 D] timing: DirectoryRefresher::refresh() 186 ms
[2026-08-06 19:47:02.308 D] directory refreshed, finishing up
[2026-08-06 19:47:02.308 D] clearing caches
[2026-08-06 19:47:02.308 D] running post refresh tasks
[2026-08-06 19:47:02.308 D] structure deleter thread start
[2026-08-06 19:47:02.340 D] timing: PluginList::fixPluginRelationships 0 ms
[2026-08-06 19:47:02.342 D] timing: PluginList::refresh() 33 ms
[2026-08-06 19:47:02.342 D] timing: OrganizerCore::refreshESPList() 33 ms
[2026-08-06 19:47:02.350 D] refreshing lists
[2026-08-06 19:47:02.352 D] structure deleter thread done
[2026-08-06 19:47:02.377 D] timing: PluginList::fixPluginRelationships 0 ms
[2026-08-06 19:47:02.379 D] timing: PluginList::refresh() 28 ms
[2026-08-06 19:47:02.379 D] timing: OrganizerCore::refreshESPList() 28 ms
[2026-08-06 19:47:02.419 D] timing: OrganizerCore::refreshBSAList() 40 ms
[2026-08-06 19:47:02.419 D] refresh done
[2026-08-06 19:47:02.419 D] timing: OrganizerCore::onDirectoryRefreshed() 110 ms
[2026-08-06 19:47:02.628 D] timing: MainWindow::checkForProblemsImpl() 5 ms

[plutocene]

Without a crashlog a guess, I think you forgot to downgrade a .dll of a newly installed mod or its incompatible.  Get https://www.nexusmods.com/fallout4/mods/87907?tab=description Verify your .dlls first. Also, get bass if you haven't  or use ba2 patcher https://www.nexusmods.com/fallout4/mods/82114, perhaps its an archive.

 

Otherwise, deactivate mods from the bottom up until the game starts.