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rusEFI for M74.9 ECUs

Custom rusEFI firmware for the Lada M74.9 engine control unit. This guide covers installing and updating the firmware. Build instructions, memory layout and tooling internals are in readme-technical-details.md.

Hardware notes and wiring: https://github.com/rusefi/m74.9

What you need

• An M74.9 ECU on the bench or in the vehicle, with the engine stopped.
• A CAN adapter connected to the ECU diagnostic CAN bus at 500 kbit/s:
  • PEAK PCAN-USB on Windows, with the PEAK driver installed, or on macOS with MacCAN installed (brew tap mac-can/maccan && brew install pcbusb), or
  • an SLCAN serial adapter such as CANable on Linux, macOS or Windows, or
  • a Linux SocketCAN interface for command-line use.
• Java, version 11 or newer recommended. On Windows the Java installation must match the PCAN driver architecture (64-bit Java for a 64-bit driver).
• The extracted rusEFI bundle. Run rusefi_updater.exe on Windows or rusefi_updater.sh on Linux/macOS to open the console.

Close any other software that uses the CAN adapter before starting. Windows Subsystem for Linux cannot load Windows PCAN libraries; use native Windows Java or expose the adapter as a Linux SocketCAN interface. On macOS, plug the PCAN adapter in before opening the console; MacCAN cannot enumerate adapters, so the PCAN selector offers PCAN_USBBUS1 (assumed) and reports a missing adapter only when the channel is opened.

Before you start: back up your ECU

The firmware keeps the OEM bootloader, calibration and identity data, but a complete backup is the only way to return to the original state. Make one before the first installation and keep it somewhere safe.

Linux/macOS, SLCAN adapter:

bin/read-flash.sh

Windows:

bin\read-flash.bat
bin\read-flash-pcan.bat

Each command finds the single connected adapter and writes a timestamped m749-full-...bin file in the current directory. Reading takes several minutes and shows progress. If it stops, run it again with the same filename and --resume. Details and options are in the backup guide.

Some ECUs require the original pairing (immobilizer) credential before they allow reading. See readme-grab-key.md for reading a .pair file from an ECU that already has one.

Check which firmware is installed

Before changing anything, confirm the console sees your ECU:

bash bin/m749-cli.sh --identify --slcan auto

bin\m749-cli.bat --identify --channel PCAN_USBBUS1

The output reports either the OEM firmware identity or an installed rusEFI version. No response usually means ECU power, CAN wiring or the bus speed is wrong. A running rusEFI image can be quiet between requests; a single timeout does not mean the ECU is missing.

M74.9 Java UI

Open the rusEFI console and select the M74.9 tab.

For an unfamiliar OEM software version, the tab shows OEM firmware installed - unknown build and please backup OEM and share it with the rusEFI team. Use Read flash... to save the backup. A recognized version still requires the loader compatibility checks before programming.

1. Select Connector: SLCAN (default), PCAN or SocketCAN. The tab queries the selected endpoint automatically and fills in Installed firmware using read-only identification requests.
2. SLCAN takes a serial port or auto; automatic selection requires exactly one adapter. SocketCAN takes an interface such as can0, already up at 500 kbit/s. PCAN lists channels in its selector and requires a choice when multiple adapters are available. Successful automatic identification pins subsequent operations to that adapter. Press Enter after editing the endpoint/settings, or use Scan / query again to retry. Identification failures are retried at ten-second intervals until an ECU responds.
3. If OEM authorization is required, choose the ECU's .pair file or original paired .bin backup under OEM credentials. An already installed M74.9 rusEFI application updates without a credential.
4. Press Flash rusEFI. The button reads Update rusEFI when a rusEFI M74.9 application is already installed. The bundled firmware file name is shown next to the button; Scan / query again re-reads it.
5. Watch the Messages tab. When it asks you to power-cycle the ECU, switch ECU power off and on while leaving the adapter connected. An installed rusEFI application updates without a power cycle.
6. Wait until Messages reports the completed upload. The tab checks the written image and the application startup after reset; a message saying the transfer finished is not yet a completed installation.

The scan and other buttons are disabled during an upload. Do not close the tab or unplug the adapter while it runs; an interrupted flash usually needs a full retry from step 4. Your calibration is preserved: the button only replaces the engine software.

For a chosen file, use the separate Read flash... and Write firmware... buttons. Identification, the bundled updater, and both file actions use the same Connector, endpoint and transport settings. Serial baud and SLCAN bus apply only to SLCAN. Receive block and STmin ms apply to all connectors; auto STmin uses the CLI's transport-specific default.

• Read flash... opens a save dialog for a full OEM .bin backup. The dialog also offers resume and already-running-helper options. Existing completed files are never overwritten. Progress, byte counts, speed and final SHA-256 appear in Messages. After a successful read the UI requests ECU reset; application return is not verified. Reading requires the OEM application's session-60 helper support, which is unavailable in the rusEFI application.
• Write firmware... opens a file dialog for rusEFI .hex/.srec or a supported OEM full-flash .bin. HEX/SREC software updates preserve calibration. OEM BIN restores replace software and calibration, preserving the connected ECU's loader, identity, pairing and storage. Only matching I812/I832/I865 profiles are supported; partial dumps are rejected. See write details and completion checks.

The buttons use the CLI transfer implementation and report progress and failures in the existing Messages control. Other operations are disabled until the transfer ends. In the embedded console, discovery is suspended and the console connection is released for direct identification and transfers; reconnect the console manually afterward.

Command-line equivalents (Windows: use the matching .bat wrappers):

bash bin/read-flash.sh "ECU backup.bin" --slcan auto --reset-after
bash bin/write-flash.sh rusefi.hex --dry-run
bash bin/write-flash.sh rusefi.srec --slcan auto
bash bin/write-flash.sh "OEM full backup.bin" --channel PCAN_USBBUS1

See the toolset review for remaining UI/CLI differences.

The Messages tab also lists the VIN and identity records read from the ECU. If the ECU does not answer, check ECU power and CAN wiring, then use Scan / query again. Unplugging and reconnecting the adapter also starts a new query.

Command-line installation and update

Current M749ACT3 software supports the I812NA01, I812TA01, I832GA01 and I865LB52 backups across three validated loader profiles. For I832, update both the uploader and firmware: older M749ACT1/M749ACT2 files cannot activate on its loader. New firmware configures an erased OEM RAM option to 384 KiB before C startup, using the existing CAN upload. Other insufficient or invalid option settings return to the resident loader without an option erase. The bootstrap passes emulator checks; physical CAN-only conversion from erased OEM options remains to be checked. See the compatibility and RAM details.

To prepare the development ECU for another first-install test, follow restore dev unit to OEM, including the saved OEM option bytes.

The same installation is available without the console UI. Linux/macOS with an SLCAN adapter:

# Check the connected ECU against the firmware file without writing anything
bash bin/m749-cli.sh --check-target rusefi.hex --slcan auto

# Install or update
bash bin/m749-cli.sh --upload rusefi.hex --slcan auto

Windows with PCAN:

bin\m749-cli.bat --check-target rusefi.hex --channel PCAN_USBBUS1
bin\m749-cli.bat --upload rusefi.hex --channel PCAN_USBBUS1

macOS with PCAN and MacCAN installed:

bash bin/m749-cli.sh --check-target rusefi.hex --channel PCAN_USBBUS1
bash bin/m749-cli.sh --upload rusefi.hex --channel PCAN_USBBUS1

Linux with SocketCAN, after configuring can0 at 500 kbit/s:

bash bin/m749-cli.sh --identify --socketcan can0
bash bin/m749-cli.sh --check-target rusefi.hex --socketcan can0
bash bin/m749-cli.sh --upload rusefi.hex --socketcan can0

For a backup, use bash bin/m749-cli.sh --read-flash backup.bin --socketcan can0.

Use the rusefi.hex or rusefi_<release>_<date>_re74.9_<signature>_<commit>_update.srec file from the bundle. Local builds use yymmdd and local when date and commit metadata are not supplied. When the ECU still runs OEM firmware and needs its pairing credential, add --pair-file ecu.pair or --immo-backup backup.bin. Follow the power-cycle prompt printed by the command. The command exits successfully only after the new firmware has been verified and has started. All options, exit codes and recovery steps are in the uploader guide.

Bench harness

Tuning

After installation, connect TunerStudio to the ECU using the rusefi_re74.9.ini file from the bundle. Tune changes are stored in the ECU's own flash and survive later firmware updates. The OEM calibration area is kept unchanged; the firmware only uploads a new calibration when you explicitly ask for it on the command line.

Troubleshooting

• PCAN not detected: install the PEAK driver, use 64-bit Java with the 64-bit driver, and close other programs using the adapter. Only native Windows Java can use the PEAK libraries; Linux CLI users can use --socketcan. On macOS install MacCAN and start Java from the bundle launcher or bin/m749-cli.sh, which put libpcanbasic_jni.dylib on java.library.path.
• No SLCAN adapter found: the wrappers need exactly one SLCAN adapter. Select it explicitly with --slcan /dev/ttyACM0 or --slcan COM5 when several serial devices are present.
• ECU does not respond: check ECU power, the CAN high/low wiring and that the bus runs at 500 kbit/s. The ECU must be powered and the engine stopped.
• rusEFI detected but flashing is disabled: the installed rusEFI build is not an M74.9 image with the update interface. Use the OEM credential route.
• Upload interrupted: the ECU may stay in its bootloader or return to the OEM application after a timeout. Power-cycle the ECU and start the upload again from the beginning.
• Old firmware files: use only the .hex and .srec files from the bundle. Do not flash .bin, .dfu or .elf files from earlier builds, and do not use generic STM32 or DFU tools on this ECU.

Status

Installation, update and flash-read transactions have been exercised on bench ECUs. Tune retention in the ECU's storage banks, recovery from power loss during an upload and long-term running behavior still need more hardware validation. Keep your backup until you are satisfied with the installed firmware.

Getting help

Questions and hardware findings are welcome at https://github.com/rusefi/m74.9 and in the rusEFI community. Include the console Messages output or the command-line output when reporting a problem.

PN

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