OPEN VAG – Free VAG Diagnostic Tool
For those working on VAG (1990–2005) with K-Line (KW1281), OPEN VAG provides a clean GUI wrapper around the kw1281test CLI tool.
Key Features
Live output streaming
Presets for Cluster, ECU, CCM, and Radio (baud rate and address set automatically)
EEPROM, ROM, and RAM dumps (saved as .bin files)
Read and clear fault codes
Adaptation channel access (mileage, keys, coding)
Radio tools: SAFE code retrieval (Delco/Clarion) and RB4 mode toggle
Custom command support
No log files, no console windows, single executable
Compatible with KKL USB cables (FTDI/CH340) on Windows 7–11. No Python or .NET installation required.
Download
GitHub:
https://github.com/ugtuner05-sys/OPEN-VagRun OPEN_VAG.exe directly.
Usage: Ignition on, engine off. Connect cable, select preset, execute command. Full cluster EEPROM dump completes in ~30 seconds via the Memory tab.
1. Physical Layer
Single wire (K-Line) + ground (L-Line optional).
Voltage: 12V system, but signals switch between 0V (low) and battery voltage (high).
Baud rates: Typically 10,400 baud (VAG default) or 9,600 baud.
Cable: Requires a K-Line interface (e.g., KKL USB with FTDI/CH340 chip) to convert to USB/RS232.
Pin 7 in the OBD2 connector = K-Line
Pin 4/5 = Ground
2. Initialization (Wake-Up)
To start communication:
ECU is asleep.
Tool sends a 5-baud wake-up pulse:
Pulls K-Line low for ~200ms, then high.
Sends address byte slowly (5 baud = 25, 55, etc.).
ECU responds with keyword bytes (e.g., 0x08 0xF7) to confirm protocol (KW1281, KW2000, etc.).
This is why ignition must be ON — ECU needs power to respond.
3. Message Structure (KW1281 Example)
Messages follow a block-based format:
BytePurpose
0
0x83 (header: 3 data bytes + address)
1
Target ECU address (e.g., 0x11 = Engine)
2
Source (diagnostic tool, usually 0xF1)
3
Command (e.g., 0x09 = Read Ident)
4–6
Data (optional)
7
Checksum (XOR of all bytes after length)
No fixed length — first byte defines payload.
Checksum: XOR of all bytes from length onward.
ACK/NAK: ECU sends 0x09 (ACK) or 0x7F (NAK + error).
4. Common Commands (KW1281)
CommandHexFunction
Read Ident
09
Get part number, coding, software version
Read Fault Codes
07
Retrieve DTCs
Clear Fault Codes
05
Erase DTCs
Adaptation Read/Save
21/22
Channel access (mileage, keys)
Group Read
29
Live data (like VCDS measuring blocks)
Dump EEPROM
Custom block mode
Read memory in 256-byte blocks
5. Block Mode (For Memory Dumps)
Used for EEPROM/ROM dumping.
Enter with 0x1A 0xA0 → ECU streams 256-byte blocks.
Tool sends ACK (0x09) after each block.
Exit with 0x1A 0xA1.
This is how tools like OPEN VAG dump cluster EEPROMs.
6. Timing & Flow Control
No hardware flow control — relies on timing.
Tool must wait for response before sending next command.
Idle: K-Line high.
Timeouts: Critical — too fast = missed bytes.
7. KW1281 vs KW2000
FeatureKW1281KW2000
Baud
10,400 (fixed)
Variable (up to 115k)
Used in
VAG clusters, older ECUs
Newer VAG (post-2000)
Block mode
Yes
Limited
8. Why It’s Still Used
EEPROM access (mileage, immobilizer, coding).
No CAN gateway needed.
Simple hardware (one wire).
Full control over ECU memory.
Tools That Use K-Line
VCDS (VAG-COM) – Ross-Tech’s official tool.
kw1281test – Open-source CLI (used in OPEN VAG).
VAG K+CAN, Carista, OBD Auto Doctor (limited).
AspectDetail
Wire
1 (K-Line)
Speed
10,400 baud
Wake-up
5-baud address
Messages
Header + command + data + checksum
Use Case
Diagnostics, coding, EEPROM dumps
Vehicles
VAG 1990–2005, BMW E36/E38, etc.
OPEN VAG simplifies all this — no need to memorize hex codes. Just click Read Ident or Dump EEPROM, and it handles the K-Line handshake, timing, and checksums behind the scenes.
