Diagnostics and DTC

Fault memory is first-class: read active and stored codes, inspect the freeze frame, read the supported list and clear the memory when the work is done.

Reading faults

• ECU List → Read DTC reads current faults from every ECU in the project.
• Read DTC List reads the full list of codes the ECU supports, whether or not they are stored.
• ECU Edit → DTC does the same for one ECU and shows the decode.
• The DTC tab header shows the DTC format, the supported status flags and the number of stored codes.

Status colours

Colour	State
Red	Active — the fault is present now
Blue	Stored — the fault was recorded earlier
Green	Not Active — supported but not currently set

The colour is a UI hint, not a replacement for the status byte. The raw status stays available in the log.

Snapshot / freeze frame

Each code can carry snapshot data recorded at the moment of failure: vehicle speed, temperature, voltage and other DIDs defined by the ECU. Expand the snapshot section under a code to see the values with units. The layout comes from the project's dtc_snapshot_data template, so unknown fields are shown as raw values rather than guessed.

Formats and databases

• J2012, ISO 14229-1 and J1939-73 decoding are supported.
• Global descriptions: <workspace>/data/dtc/codes.json or .txt.
• Project-local descriptions: Project Properties → Local DTC File (.json or .txt).
• JSON uses a codes map; TXT uses one CODE description line per code. Lines starting with # or ; are ignored.
• Codes may be P, C, B or U followed by 5 or 7 hex characters.
• If a file is missing, its path in Project Properties is highlighted in red.

Clear and export

• Clear DTC clears the selected ECU; the ECU List button clears every ECU. Both ask for confirmation.
• Save a project dump (ECU List → Save/Load → Save Data) before clearing if the fault history matters.
• The ECU table itself can be exported to CSV (separator ;, trailing ;) from the ECU List.

Practical notes

• Read the supported list once and compare it with the current fault list: codes outside the supported list are often vendor extensions.
• Clearing faults does not fix them. Save the table and the snapshots before clearing.
• If a code returns immediately after a clear, the fault condition is still present; investigate the signal rather than repeating the clear.
• A code without a description is still read and exported correctly; only the text is missing.

Related

• Read and clear faults
• Reports and export
• Workspace and projects