Select Monitor Adapter
Subaru Diagnostic Ports
How to build a PC adapter

Engine Control Unit (ECU)
Reading Error Codes
Reverse Engineering
ROM images

Transmission Control Unit (TCU)
Reading Error Codes
Reverse Engineering
Power Mode
ROM images

Other Control Units
Air Conditioning Unit
4WS Control Unit
Cruise Control Unit

OBD2 Information
Select Monitor Cartridge

Links to other sites

Custom TCU Development

Diagnostics and Datalogging for Subaru SVX

This site is about connecting a computer to your Subaru. I'm an SVX enthusiast and that is the main focus of the project. But the much of the information here also applies to other Subaru models with JECS ECUs produced between 1992 and 1996. I started playing with the ECU in April 2007 after being inspired by the research of others. I posted my findings on the Subaru SVX World Network and other members have since joined the project and contributed their time and expertise.

So far, we have learned how to communicate with the ECU (Engine Control Unit) and TCU (Transmission Control Unit). Using a laptop and special software, values such as speed, temperature and rpm can be extracted from these units for diagnostics and datalogging purposes.

We have also managed to modify the firmware that controls the operation of the ECU and TCU. It is possible, for example, to change the air:fuel ratio and ignition timing in the ECU, and the gearshift maps or line pressure in the TCU.

The remaining challenge is to better understand the maps, tables and calculations in the firmware so that we can be confident of the accuracy of the paramenters that we extract and the effect of any changes that we make.

Click on the links in the blue area on the left side of the page for information about the project.

There is an ongoing thread on the SVX Network where we discuss our progress. I don't have a chance to update this website very often, so always look to the thread for the most up to date information
Click here to view the thread

If you are working on a similar project, or wish to discuss any of the information presented here, please drop me an email or join in the thread on the SVX World Network.