Read and write values

Reading is safe; writing changes the ECU. The workflow below keeps a copy of the original value and verifies the new one.

Read

1. Open the ECU in ECU Edit.
2. Info tab → Refresh Info reads the info group.
3. Parameters tab shows the rest of the project-defined DIDs.
4. Right-click a row for Read (Ctrl+R) and Copy to clipboard (Ctrl+C). Ctrl+A selects all; Ctrl+click / Shift+click selects multiple rows.
5. ECU List → Read All reads every parameter of every ECU in the project.

Write

1. Open Writable Values. It lists parameters with writeable: true and a View.
2. Change the value. The editor shows the decoded value and the raw bytes that will be sent.
3. Confirm the write in the dialog.
4. Wait for the positive response and read the value back.

Writing uses UDS 0x2E. If the parameter has a separate write_auth level, that level is used for the write. A parameter in group ioctl with writeable: true is available both here (0x2E) and in IO Control (0x2F).

Security access

If the parameter is protected, the project must define an auth level and a Seed2Key DLL in data/auth/. The application performs the seed/key exchange automatically before the write. A rejected key appears in the log with the negative response code.

Manual seed/key work is available in UDS Tools.

Before a write

• Save a project dump (ECU List → Save/Load → Save Data) or export the table to CSV.
• Confirm the target ECU: the same DID can mean different things on two ECUs.
• Confirm the session and security level if you are writing outside the normal editor.
• Do not write while the vehicle is being flashed or while another tester holds the session.

A positive UDS response means the ECU accepted the request. It does not prove that the value is correct for this vehicle. Read it back and compare with the expected behaviour.

Related

• DID parameters
• UDS toolset
• File formats