Fix crash at launch

This guide is designed to help players suffering from game crashes at launch.

Introduction

For the moment I've only encountered an issue related to antivirus behavior.
If you found others, feel free to share them in comment section followed with explanations how to fix the matter.
I'll try to keep this document up to date as much as possible.

Crash identification

Forza Horizon 4 crashes on startup after a fresh install.

Steps

• Open Steam app.
  
• Open Library tab.
  
• Select Forza Horizon 4.
  
• Click on Play button.

Expected result

• Steam Play button updates itself into a Stop button.
  
• Forza Horizon 4 bootscreen opens.
  
• Few seconds pass.
  
• Forza horizon 4 boots into a window.

Actual result

• Steam Play button updates itself into a Stop button.
  
• Few seconds pass.
  
• Steam Stop button updates itself into a Play button.

Identify crash exception code

• Tap Windows key on your keyboard.
  
• Type « Event Viewer » then open suggested program.
  
• Click on « Windows Logs ».
  
• Double click on « Application ».
  
• Sort by date.
  
• Look for recent error log caused by « Forza Horizon 4 » program.
  
• Check its exception code.

Possible cause: shell code injection

Explanations

My crash exception code was 0xc0000005 . According to Windows support, it can be caused by an illegal program access from another program.

This kind of issue can be caused by your antivirus. As a reminder, its role is to check that noprogram running on your computer is doing anything dangerous to your operating system or to your computer data.
To make sure of it, it often wraps processes or even look into it through code injection.

Code injection is also a strategy used by game hackers with various purposes that can be from enabling hidden features within the game, to inject mods, to add cheats, etc.

So in order to prevent illegal code injection within the game, it seems Forza Horizon 4 detects that something « forbidden » is happening and simply quits / crashes itself. The fix is simply to prevent your antivirus from injecting code within Forza Horizon 4 program execution.

Note that this kind of behaviour can happen to other games so I assume this fix could be applied to them (while hoping they suffer from this very issue as well).

Program

It is also possible that the issue is caused by a different program that behaves like the "shell injection code" of your antivirus, which ends up monitoring or altering your game process and simply causes it to crash.
There can be plenty of programs that acts like this and I won't be able to help you on this one since everyone have different kind of software on their computer so the list would be too difficult to maintain.

Antivirus

Most of the time disabling your antivirus could do the trick but keep in mind it is not recommended to do since your system will be completely vulnerable.

Instead try to look into your antivirus documentation for explanations on "how to disable shell code injection" or "how to add shell injection program exception".

Comodo Firewall

I’ve only tried this with Comodo Firewall so here are the steps to follow to fix this.

Steam

• Open « Steam » program.
  
• Select « Library » tab.
  
• Right-click on « Forza Horizon 4 » entry then click on « Properties ».
  
• Click on « Local files ».
  
• Click on « Browse » button.
  
• Close « Properties» window.

Windows explorer

• Copy path of your « Forza Horizon 4 » folder.
  
• Close « Windows explorer » window.

Comodo firewall

• Open « Comodo Firewall ».
  
• Click on settings.
  
• Expand « Advanced protection » in left panel.
  
• Click on « Miscellaneous ».
  
• Click on link in « Do not detect command injection in these applications ».
  
• Click on « Add » button then select « File ».
  
• Browse up to « ForzaHorizon4.exe » located within your own Forza Horizon 4 installation folder then select it (you can paste the path you've copied earlier in the address bar).
  
• Click on « OK » button (closes exception window).
  
• Click on « OK » button (closes settings window).

Steam

• Open « Steam » program.
  
• Select « Library » tab.
  
• Select « Forza Horizon 4 ».
  
• Click on Play button.

Norton

Not tested.
It is possible your Norton program blocked your game for some reason. Try to whitelist it following these steps.

Norton

• Open your "Norton device security" product.
  
• If you see the "My Norton" window, next to "Device Security", click Open.
  
• In the "Norton" product main window, click "Settings".
  
• In the "Settings" window, click "Firewall".
  
• On the "Program Control" tab, select the program that you want to allow access to the Internet.
  
• In the Access drop-down list for the program entry, click "Allow".
  
• Click "Apply".

Steam

• Open « Steam » program.
  
• Select « Library » tab.
  
• Select « Forza Horizon 4 ».
  
• Click on Play button.

Windows Defender

As far as I can tell, there shouldn't be any issues.
If you only have Windows Defender as an antivirus, it is possible a different program tries to alter / monitor the Forza Horizon 4 process.
Check a look in Resources section for more informations on how Windows Defender deals with Shell code injection (technical blog post).

Resources

• Official Forza Horizon support game not launching[support.forzamotorsport.net]
  
• Comodo Firewall add program command execution exception[help.comodo.com]
  
• Windows 0xc0000005 exception code support[support.microsoft.com]
  
• Norton support allow program[support.norton.com]
  
• Windows Defender cross-process injection blog post[www.microsoft.com]

[HeartOfChorizo]

@adceng glad this helped you.

[adceng]

It worked for me also !!! I have Comodo Firewall causing the problem. Many many thanks

[Alpha]

my hero tysm slow clap award

[çılgın]

thx

[HeartOfChorizo]

@SakuMyao I feel this seems out of scope for this guide and beyond my knwoledge.
Please read this guide once again, or have a look into Forza's forums: you might be able to find one or two things. I hope you'll find a solution to this.

[SakuMyao]

Still not working, playable for a week with zero problem, smooth and nice then got crashed every game started, please help

[HeartOfChorizo]

As far as I know Windows Defender shouldn't have any impact on the game.
I'm updating the Resources section with additional documentation related to Windows Defender.

[nintendo switch]

i use windows defender as my antivirus tho, do you know how to solve this???

[mohduves104]

bro now also it is not working. Please help me!!!!!

[Skydancer]

THX