FastECU documentation
FastECU reads, edits and writes the software of Subaru ECUs and TCUs, logs live data and helps you understand what is in a ROM. These pages explain how to set it up and use it.
Getting started
OverviewWhat FastECU is, what it does and which pages it has.
InstallInstalling FastECU on Windows or Linux, and keeping it up to date.
Account, plans & license keyCreating an account, the 14-day trial and activating the license key in the app.
Hardware you needK-Line cables, J2534 devices and the FastECU wireless adapter.
First stepsPick a car, open a ROM, find its definition and edit a table.
Connecting to the car
Vehicle & protocolsChoosing the car and the protocol that talks to each control unit.
Ports & adaptersChoosing the serial port or adapter and sharing it between functions.
Trouble codesReading trouble codes with the supported DTC protocols.
DataloggingRecording, plotting and analysing live data.
Reading & writing ROMsThe ROM tab: backups, test write and write, and how the kernel gets into the ECU.
Bus monitorWatching and sending K-Line and CAN traffic.
RecoveryBench recovery of bricked or locked ECUs through boot mode or BDM.
Tuning
Definitions & loading ROMsOpening ROMs, finding their definitions and checking them.
Calibration editorEditing tables: grid, selection, set value, interpolate, 3D and bump finder.
Changes, history & tune filesUndo, revert, snapshots and sharing a tune without the ROM.
Datalog trace & correctionsDrawing a datalog on a table and proposing knock, AFR and boost corrections.
MAF scalingCorrecting the MAF sensor curve from a datalog.
Injector scaling & latencyFitting injector flow and dead time from a datalog.
Virtual dynoPower and torque curves from full-throttle pulls.
Compare ROMsTable-by-table differences and porting a definition to another ROM.
Hex editor & checksumsRaw bytes, table finder, ROM structure and checksum checks.
Reverse engineering
DisassemblerImporting a ROM, reading its code, decompiled C and flow charts.
Finding & defining tablesHow to make a definition for a ROM that has none.
AI assistant
Setting up the assistantTurning on the local MCP server and connecting Claude Code or another client.
What the assistant can doReading ROMs and logs, proposing edits, trouble codes and reverse engineering help.
Remote control
How remote control worksServer and client roles, the broker and what is protected.
Pairing & using itStarting a session, tokens, hosted or own broker, and reading and writing remotely.
FastECU Remote ClientThe small companion app for the person with the car.
Help
TroubleshootingCommon problems with adapters, license, definitions, logging and flashing.
FAQShort answers to common questions.
Questions?
Ask on the support forum or write to info@fastecu.fi.