When a game is as old as Gran Turismo 4 – which just celebrated its 18th birthday in February – you’d assume that everything there is to know about it has already been dug up. The GT4 news that made the rounds on Twitter last weekend was all the more surprising: a modder discovered cheat codes in the 2005 racing simulation that nobody knew about before. That’s how it happened, according to the person who made it possible.
In case you missed it:
Before we get to that, some background on the cheats themselves. They’re pretty standard, but practically blow the game wide. One gives you 10 million credits, while others let you automatically earn “gold” on any license test or race event with a simple keystroke.
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The catch is that these codes only work after 365 days have passed in-game, which either requires hours of normal gameplay ahead of time, or forces the player to track progress using tricks like buying aftermarket wheels or entering and Speed exit from license tests.
The breakthrough happened today, not a decade ago, because just a few years ago, a modder and data miner named Nenkai was able to figure out what lurks inside developer Polyphony Digital’s custom programming language. I spoke to Nenkai recently; In his own words, this is how the discovery came about:
So GT4 (and all games since) runs a custom, compiled scripting language called Adhoc, which first had to be fully reverse engineered to understand what the game was doing. It sits on top of the PS2 code to make programming the game easier. So in 2020 I figured it all out, and it felt like opening Pandora’s box, people including me disassembled the games and randomly looked at bits of it until some weirdly specific numbers that happened to be keycodes , found along with “command checks”, found debug menus when compositing, a special menu was also found for GT4.
And that was basically the end for a good while.
As I’ve been making more GT4 modding tools lately and TheAdmiester is using them, I figured I’d tackle a project to reverse engineer all the compiled code of the GT mode script and reverse engineer it into compilable source code to enable logic-based modding. Since that was going pretty well, I happened to notice some more codes that I wasn’t aware of, nor documented anywhere, so I booted [emulator] PCSX2 and tried to activate one of them and it didn’t work.
Nenkai then attempted to activate the codes using a metaphorical second controller in the PCSX2 emulator, as GT4’s special menu requires it. That didn’t work either, leading him to believe they weren’t actually implemented. Until he noticed something:
The catch was a sneaky check on game day. So I went ahead and edited my save with my save editor to advance days and tried again and heard this noise. Later I also tested with the Tourist Trophy, which internally is almost exclusively GT4 camouflaged, and that worked too.
Image: Sony Interactive Entertainment
That’s right: These cheats also work in Polyphony’s Motorbike Racer Tourist Trophy! If you want to try them yourself, here’s what you need to do about The Cutting Room Floor. Again, 365 days must have passed in-game before they work:
10,000,000 Credits (GT Mode Screen): Select, Left, Right, Right, Down, Up, Up, Left, Down, Up, Right, Left, Down, L1, R1, Select
Pass any license (license selection screen): Select, R1, Select, R1, Select, L2, L2, R2, R2, L1, Select, L1, Select
Gold for a specific license test (license test selection screen): Select, Select, R1, R2, L2, L2, Select, L1, R1, Select, R2, L1, Select
Gold Any Event (Event Price Selection Screen): Select, L1, Up, Up, Select, R1, Down, Down, Select, L2, Select, R2, Select
An additional code can be used in the mission hall, which also adds 10,000,000 credits. It’s probably implemented incorrectly and should allow you to complete every mission instead. The code is Select, R2, Select, R2, L1, L2, L2, Select, L1, R1, Select, R1, Select.
But why are they in the game at all? Of course, without confirmation from the developers, we’ll never know. As with many cheat codes, it’s possible that they were originally used for internal testing. Maybe they were put behind a day check for release so players can’t get everything right from the start.
Gran Turismo titles had never been known to have cheats – even back when this type of practice was more common – so you can imagine how valuable that knowledge would have been at IGN or GameFAQs in 2005. Today the effect is different, but at least you can save yourself a little time on the next playthrough. No more needing to B-spec the pesky Nürburgring 24 Hours to snag Formula Gran Turismo.
