K-Performace
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« on: December 09, 2025, 09:50:21 AM »
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I bought a MK5 for my wife, and now I want to flash the car back to stock because the software on it drives really strangely, and that can’t be right.
However, I’m unable to write an original file. Kess and MPPS abort immediately over OBD.
Then I opened the ECU and read it in boot mode with KTAG. I bought the correct stock file online and tried to write it via boot mode — again without success! It always fails at 34%.
I even bought a complete KTAG backup, and that also won’t write.
According to the seller, a tuner wrote a mod on it with pops & bangs via cruise control.
Did he damage the ECU, and do I have to keep driving with this crap now?!
I will upload both files.
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Dande
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« Reply #1 on: December 09, 2025, 12:18:00 PM »
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The ECU may be damaged after many writes. The ori file looks fine.
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K-Performace
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« Reply #2 on: December 09, 2025, 01:12:18 PM »
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Yes, I thought of that too. I also have some experience with med9, but I've never encountered this before! I've tried writing 5-6 full backups via boot, but it always aborts, sometimes at 9%, 35%, or 62%, and always at the same point if I try repeatedly. Nothing works via OBD at all. I always get an error message: "Incorrect security code!" I can do whatever I want, it just won't let me! WinOLS tells me that the read data has a checksum error. If I only correct the error, it still won't let me write the file. If I ignore the checksum and only change one bit, it still won't let me write. If I try writing everything unchanged, it works every time and the car runs again! I think it might be due to a custom code that the tuner installed, where they inserted the "pop and bang" code to lock everything. But I don't know what to do now. Can I simply transfer the EEPROM to another control unit so I don't have to disable the immobilizer? Then I'll probably have to get a replacement control unit! The car is undrivable; it's running way too lean.
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BlackT
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« Reply #3 on: December 10, 2025, 03:43:41 AM »
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For now I suggest you to do full write eeprom and flash from another ECU. (you will need to disable immo)
Than you will be sure that ECU is okay
So you can drive a car until you find solution how to transfer old immo data, or pair new immo data to your car
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Dande
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« Reply #4 on: December 10, 2025, 10:02:18 AM »
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I found the protection. Send me the eeprom
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K-Performace
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« Reply #5 on: December 10, 2025, 01:11:05 PM »
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This is all from the control unit. I hope this helps you.
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Dande
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« Reply #6 on: December 11, 2025, 10:18:12 AM »
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First write eeprom, then flash. Let me know.
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K-Performace
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« Reply #7 on: December 11, 2025, 12:33:03 PM »
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Hey, thanks a lot for your effort. I've now written the EEPROM correctly. The flash write aborts at 18%. Maybe the image will help you see which sector it's affecting.
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Dande
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« Reply #8 on: December 11, 2025, 01:14:16 PM »
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The ecu is damaged.
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