Vehicle & protocols

A protocol is the language FastECU uses with a control unit. Choosing the right car on the Vehicle page picks it for you.

Choose the vehicle

1. Open the Vehicle page.
2. Pick Manufacturer, Model and Variant. Each select depends on the one before.
3. A summary below the selects shows the ECU, TCU and BIU protocol that the matching pages will use. The ECU protocol also shows in the status bar.

Your choice is remembered when you restart the app.

Control units: ECU, TCU and BIU

The ECU, TCU and BIU pages share one layout: a connection card (protocol, port, link state) above tabs.

Using another protocol than the car's

The connection card's protocol picker defaults to the vehicle's protocol, but you can pin a different one. This is useful when:

• the catalog entry for your car lists no TCU or BIU protocol,
• you want to talk to a unit directly without choosing a vehicle at all.

Picking another vehicle on the Vehicle page drops the pins you made.

How the ECU gets its flash kernel

To read or write the ROM, FastECU needs a small program, a kernel, running inside the control unit. There are two cases, and which one applies depends on the protocol:

• Uploaded: FastECU loads its own kernel into the ECU's RAM through the ECU's bootloader. This is used for the Denso SH7055/SH7058/SH7059 and 16-bit K-Line ECUs.
• On-board: the ECU or TCU already carries a kernel in its ROM. FastECU only unlocks it and starts it, nothing is uploaded. This covers all Hitachi ROMs, the Unisia Jecs K-Line ECUs and several newer Denso and Mitsubishi units.

You do not choose this yourself, it follows from the protocol. See Reading & writing ROMs for how it is used.

Which protocols exist

FastECU covers Denso, Hitachi, Mitsubishi and Unisia Jecs ECUs, and Hitachi and other TCUs, over K-Line and CAN, including EcuTek-modified ROMs for several of them. The full list is long and changes as protocols are added or tested.