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Subaru's are popular with DIY & performance professionals with lots of modifications available. There's several software packages that allow various task to read and write data to the cars computer. Some diagnosis is possible with procedures that Subaru have built right into the dashboard.
¶ Built In
The cars have built in green connectors to enable the so called ‘test mode’ behind the passenger foot well carpet near centre of the car. When connected the radiator fans and automatically cycle on and off to confirm operation and some self tests are performed. More tests are available with these connectors joined when using Subaru Select Monitor or Free SSM. Typically this mode is used by the dealership to check functionality when a new vehicle is received. Don't drive with these connected.
You can read diagnostic trouble codes right from the dashboard - see the control systems notes for more information. The air conditioning system can also be diagnosed from its front panel, see the control systems notes for more info.
¶ After-market Logging and Tuning Tools
¶ Overview
There are a variety of hardware required to connect to the cars control systems, see the control systems page for more information on the protocols. Please note that any store links are provided only as examples and are not sponsored or endorsed. Scroll down the page for more info on each application.
¶ Applications
| Software | OS | Interface Hardware | Configuration Note | Note | |
|---|---|---|---|---|---|
| RomRaider Logger |
Read and reset engine trouble codes Read data from the engine and transmission computers |
Windows, Linux | I1 | C2 | Regular logging |
| I2 | C1 | Fast logging | |||
| RomRaider ECU Editor | Edit ROM's to design remapped tunes | Windows, Linux | - | - | - |
| FreeSSM |
Read and reset engine trouble codes Read data from the engine and transmission computers Run component tests i.e. turn radiator fans on and off |
Windows, Linux | I1 | C4 | Build the latest FreeSSM source code to use with Tactrix OpenPort |
| Cascade |
Read and reset engine, transmission, ABS trouble codes Read some parameters from engine, transmission, ABS, BIU computers |
Windows | I3 | C5 | Can reset ABS brake & BIU body computer diagnostic trouble codes (DTC's) |
| ECU Flash | Read and write new ROM's to your engine computer to remap tunes | Windows | I2 | See section below | |
| BtSsm |
Read and reset engine trouble codes Read data from the engine and transmission computers |
Android | I5 | Many connectivity options are supported including Bluetooth (I5), USB OTG (I4), USB Tactrix (I2) |
¶ Interface Hardware
| I1 | FT232RL K-Line FTDI INPA compatible USB cable | Amazon, OBD Shop |
| I2 | Tactrix OpenPort 2.0 with USB cable or SD card | Tactrix |
| I3 | RS232KL K2L901 K-Line VAG USB cable | OBD Shop |
| I4 |
USB On the go (OTG) adapter. The Android device must be OTG compatible. |
|
| I5 | Refer to BtSsm compatibility page | Link |
¶ Configuration Notes
| C1 | Select ‘SSM’ 'CAN Bus’ under the Communication Settings menu from the RomRaider Logger Settings menu. |
| C2 | Select 'SSM' 'K-Line’ under the Communications Settings menu from the RomRaider Logger Settings menu |
| C3 | Select ‘Enable Fast Polling mode’ from the RomRaider Logger Settings menu |
| C4 | Be sure to select and test COM ports from the FreeSSM opening screen |
| C5 | Sometimes multiple attempts may be required to connect to the car computer selected |
¶ FreeSSM
FreeSSM is an excellent open source software for Windows and Linux computers requiring just a J2534 or Tactrix cable. The software allows check engine trouble codes to be read and reset or to read individual parameters from the engine and transmission computers. Some diagnostic tests are also possible with the test mode connectors described above are connected.
¶ v1.2.5
This version is available to download from a number of websites, for example SourceForge has a copy.
¶ Development (Latest)
To run the latest version of FreeSSM which supports Tactrix OpenPort you can build the software from source code on your computer using our FreeSSM build instructions.
¶ RomRaider
A free go to tool for all Subaru enthusiasts ideal on a Windows laptop with a J2534 or Tactrix USB. RomRaider is actually two apps Logger & ECU Editor. Logger allows similar and more functionality to Free SSM albeit without the system tests but does allow logs to be charted, stored to disk or even started and stopped via the rear window defogger siwtch.ECU Editor allows maps controlling engine management to be viewed and modified, this is generally of interest to people wanting to tune their engine computer for different behaviour or to suit other modifications such as intake, injectors, turbo or exhaust.
RomRaider is not easy to set-up as several definition files must be installed, see our RomRaider page for our easy set-up guide and to get started with RomRaider.
¶ ECU Flash
Required for reading and writing (flashing) ROM's to the cars engine computer generally in conjunction with the Tactrix USB adapter.
Warning - not mentioned in the documentation. If for any reason a flash fails do not turn off the car's dashboard - this will ‘brick’ the computer and make the car undriveable although the dashboard can be turned on error messages may be shown and the car will not start. The ECU can be recovered by sending it to Tactrix, San Francisco USA or one or two other companies including in Australia. You can also build this electronic circuit to recover a bricked ECU using Renases SH Boot Mode in ECU Flash see these notes, notes, notes.
¶ ScoobyRom
ScoobyRom is fantastic to reverse engineer Subaru ROM files and find 2D and 3D tables that may not be defined with RomRaider or ECUFlash definition files. To get ScoobyRom running on your Windows computer see our build guide and for usage tips see our using ScoobyRom page.
¶ Cascade 0.9.3
A free software to read and reset codes on the engine, transmission and ABS computers with a suitable cable. It is useful as other tools cannot reset ABS codes. For general information see this forum page.
Cascade requires a K-Line FTDI USB cable or a K-Line+CAN FTDI USB Cable to operate.
¶ BtSsm
A paid Android app for Subaru enthusiasts to view real time data. Check out their homepage at https://www.btssm.com/.
¶ Subaru Select Monitor
¶ Subaru Select Monitor III
Also known as SSM-III or SSM3 this is the tool the dealerships use whilst working on 2005 - 2009 Subaru cars. Whilst there are dubious downloads of this product online they are not recommended and require expensive hardware to function. Unless you prefer to purchase from the manufacturer this is many many thousands of dollars. It's likely more efficient to go to the dealership if you need to occasionally register new keys to the immobilizer or such.
¶ Subaru Select Monitor IV
This version of SSM, SSM-IV or SSM4 will not work for pre-2010 Subaru vehicles.
¶ Tactrix Open Port
Sometimes incorrectly referred to as a cable the Open Port is a hardware adapter that connects into the vehicle onboard diagnostics (OBD-II) port. It's a clever device that allows a laptop to connect with Subaru specific parameters related to the engine or transmission. Required for reading and writing ROM data when tuning the vehicle.
As a bonus this also works to diagnose Toyota vehicles with Toyota Techstream software.
¶ Log direct to SD-card
Why setup a laptop each time you want to log? Tactrix can continuously log data to SD-card if a file called logcfg.txt is stored on the SD card. You can automatically generate a logcfg.txt file from an existing RomRaider logging definition file with the utility @ http://romraider.com/logcfg/. For more information and samples of how logcfg.txt can be used see your installation directory, typically at C:\Program Files (x86)\OpenECU\EcuFlash\samples\logging.
¶ CAN logging for high speed data
OpenPort can provide parameter data at high speed if CAN logging is enabled on the ROM. logcfg.txt can then be configured with type=ssmcan (or in RomRaider selecting CAN as the comms protocol). Note that there is a patch that must be applied to the ROM and flashed to the ECU.
The patch can be applied using ECUFlash (exc. Legacies) via the ‘Subaru CAN Enhanced RAM parameter logging’ checkbox or a patching service such as this one (some Legacies supported) with the ‘CAN A8 handler patch’. More info can be found at this RomRaider thread.
¶ MegaLogViewer HD
MegaLogViewer HD is powerful software to analyze log data collected by RomRaider, Tactrix, BtSSM or other data loggers. Generate line charts, scatter charts and histograms to see the relationship between any logged value on the X, Y or Z axis. There's plenty of options to make this a good option for serious analysis. Note that the free edition supports up to only 400 rows of data. The software is related to the MegaSquirt tuning family however can be used with data files from any other logger.
¶ FastECU
A new open source ROM reading & flash tool from Syvanen Motor Sport that enables editing tables and logging data. As of April 2023 it includes functionality to view and edit Body Integrated Unit (BIU) settings which is the first time this has been achieved by open source tools.
https://www.syvanenmotorsport.fi/forum/index.php
https://github.com/miikasyvanen/fastecu-oem
¶ ROM Disassembly
This is an advanced topic.
The success of RomRaider is because it exposes tables and parameters that are not reported by standard OBD-II protocols. However these need to be defined for tools such as RomRaider or ECUFlash to use them. Locating tables, extended parameters and ROM logic is a complex process requiring software development tools and experience. You can read more about this on these RomRaider posts using tools such as the expensive IDA pro or the open source Ghidra.
¶ IDA Pro
¶ Ghidra