a3c turns on hidden Audi and Volkswagen features, changes the MMI language, reads fault codes and handles SFD. You see every change before it is written, and one click puts it back.
From a one-click function to a single bit of long coding. a3c shows what is already on in the car and what will change.
Ready-made functions
MMI language, CarPlay, radio logos, lights, sounds, instrument cluster. Each has an honest status: verified on a car or a map only.
Preview and rollback
Every changed byte is visible before the write. A backup is made automatically, and history keeps before → after.
Coding, bit by bit
Long coding for any control unit: HEX and single bits, with what will change highlighted.
Fault codes, decoded
Fault codes from every unit with failure type, status, mileage and time. Clearing only after you confirm.
SFD under control
Unit protection status, the activation request and token entry right in the app.
Unit passport
Part numbers, software versions and FAZIT for every unit after a single scan.
Verified on a car
Russian in the MMI of a Chinese Audi A3
The function swaps the Cantonese slot in dataset 720C for Russian and recalculates the checksum. Length and all other bytes stay the same, so rolling back is a plain write of the original from the backup.
Navigation, voice prompts and SMS are a separate function. The first screen, the main menu and voice control stay in other languages: the Asian firmware has no such resources.
SFD on unit 5FMMI restarts ~40 srollback from history
How it works
Three steps from adapter to new feature
No wiring diagrams or checksum calculators — a3c checks everything itself.
1
Connect an adapter
ELM327 over Bluetooth, Wi‑Fi or USB, or a DoIP cable. a3c checks the adapter, the link to the car and the voltage.
2
Pick a function
a3c reads the units and shows what is on, what can be turned on and which units wait for SFD.
3
Review and write
Preview, backup, write. Changed your mind? Put it back from history.
Cars
What is supported
The function catalogue updates from the server: new cars and functions arrive without an app update.
AudiVerified on a car
A3 8Y
Sportback and sedan with MIB3, from 2020
Russian MMI and navigation
Multimedia, lights, doors, cluster, sounds, body
Service procedures and diagnostics
VW GroupService procedures
MQB and MQB Evo
Audi, Volkswagen, Škoda, SEAT, CUPRA
DSG adaptation DQ200 and DQ381
Throttle adaptation, parking brake service mode, TPMS reset
Diagnostics for every unit
Compatibility with a particular car, unit and firmware is not guaranteed: a3c checks the unit and will not offer a map that does not fit it.
Adapters
Use what you already have
a3c works with inexpensive ELM327 adapters and with a DoIP cable.
Adapter
Link
What for
ELM327 Bluetooth LE, e.g. Vgate iCar Pro
Bluetooth
Everything: reading, coding, faults, SFD
ELM327 Wi‑Fi
Wi‑Fi
The same; the Mac joins the adapter's network
ELM327 USB
USB
The same, over a cable
DoIP cable (ENET)
Ethernet
Fast reading and writing
Pricing
Diagnostics for free, changes by subscription
a3c Pro is a monthly or yearly subscription in the Mac App Store. See the price on the app page.
a3c
Freeno sign-up
Unit scan and passport
Fault codes and clearing
Adaptations
Diagnostic functions
Simulator to learn without a car
a3c Pro
For changes
Subscriptionmonthly or yearly, in the Mac App Store
a3c does not ask for an account. Server requests carry only the app, macOS and language versions: no device ID, no VIN, no Apple ID. The VIN and car data stay on your Mac.
Only to download the function catalogue the first time. After that a3c works offline: the catalogue is stored on the Mac, and the link to the car does not use the internet.
Which adapter should I get?
Any ELM327 with Bluetooth LE, Wi‑Fi or USB — for example, Vgate iCar Pro. A DoIP (ENET) cable is faster.
What is SFD and where do I get a token?
SFD protects control units on newer VAG cars: without activation a unit refuses changes. a3c shows the request string and accepts the token; the token itself comes from an official or third-party activation service.
Can a write harm the car?
Any write to control units carries risk. a3c shows changes in advance, keeps a backup and lets you put things back, but the decision to write is yours. Read the safety rules first.
What data does a3c collect?
No personal data and no identifiers. The server sees only the app and engine versions, the macOS version and the language. Details are in the privacy policy.
Can I try it without a car?
Yes: a3c has a simulator — a whole car in memory. You can learn every screen with zero risk.
a3c
