The NHW10 uses the ISO 14230-4 Keyword Protocol 2000 and a standard 16-pin OBD-II connector located on the right hand side underneath the steering wheel. But while some OBD-II scanners on the market do support that protocol, most aren't aware of the specific parameters or actions available on an NHW10 and thus simply do not recognise the vehicle. 

Fortunately, Valentin8080, a car enthusiast from Russia, has build a free software, TECU 3, that uses the CAN Bus based, K-Line adapter to scan and perform actions on the NHW10.

So, here is the simplest and most affordable way of scanning the car at the moment:

What you will needEdit

You will need 4 things:

  • Car - A first generation Toyota Prius built between 1997-1999 (NHW10, aka Prius Mk1)
    $(KGrHqUOKowFHkG0bFEbBR7jLgSStw~~60 12

    VAG COM K-Line to USB adapter

  • Computer - A computer built within the last 8 years or so running a version of Windows (XP, Vista, 7, 8). A laptop is preferable as it more convenient to use in the car.
  • Adapter - VAG COM - an ISO 14230 K-Line to USB adapter. An easiest way to get one is to search for "VAG COM K-Line to USB adapter" on eBay or at your favorite auto website. It should cost around $10 - $15 with shipping.
  • Software - TECU 3 (version: This is a free software built by a Russian car enthusiast Valentin8080. TECU 3 is downloadable from his site ( Unfortunately the site is mostly in Russian, but if you have trouble finding the download link, you can download directly from:  Please note that later versions of the software are now available, however the instructions contained here have not yet been updated and therefore only cover version, so please get this version if possible. 

Connecting the Adapter to your ComputerEdit

  1. Connect the VAG COM adapter cable to a spare USB port of your computer.
  2. Wait for the new hardware to be installed by Windows or install the required driver manually from a disk that comes with the adapter. Wait for the "Your hardware has been installed successfully" message to appear on your task bar.
  3. You can now determine which number virtual COM port the adapter has been assigned to.
    1. Open Windows Control Panel
    2. Choose "System and Security"
    3. Choose "System"
    4. Choose "Device Manager"
    5. Expand "Ports"
    6. VAG Com device should be listed under with a corresponding port number in brackets. Eg: COM27

It's a good idea to always connect the adapter cable to the same USB port of your computer. Connecting it to a different USB port will most likely mean that the connection will change to different number COM port and this will require TECU to be reconfigured.

Setup TECU 3Edit

  1. Extract the TECU 3 software from the package you have downloaded ( TECU 3 does not need to be installed, it just needs to be extracted to any location on your hard disk, for example: C:\TECU3
  2. TECU 3 is a Russian language Software so it requires Windows locale to be set to Russia. To Switch your Windows locale to Russia:
    1. Open Windows Control Panel
    2. Choose "Change Display Language"
    3. Go to "Administrative" tab
    4. Press on "Change system locale..."
    5. Select "Russian (Russia)"
    6. Click Ok
    7. Restart your computer.
  3. Configure TECU 3 to use your adapter
    1. Start TECU 3 by running tecu.exe from the folder where the software was extracted to.
    2. Press Ctrl+K on the main screen of TECU to bring up connection settings screen
    3. In the Адаптер drop down, select VAG COM
    4. Also set a COM port corresponding to the one determined in section above.
    5. Click the blue Save button.

After installing the English translation files (below), it is possible to use TECU 3 without having the locale set to Russia. The only down side is that all Cyrillic (Russian) letters will appear as strange symbols and the text will not be readable. However, most of the software will still be useable. To switch your locale back to your home country repeat step 2 and select your original country. 

English TranslationEdit

Default install of TECU 3 will display all NHW10 computer parameters and errors in Russian. In order to get these to display in English you need to install translated versions of the TECU 3 resource files. To do this:

  1. Make sure TECU is not running. 
  2. Download the following 3 files: 
  3. Replace TECU 3 resource files with english versions:
    1. Extract all files from to the following directory in your TECU 3 installation: ECU\TOYOTA\HVBAT1\00 making sure to replace all the files that are there.
    2. Extract all files from to the following directory in your TECU 3 installation: ECU\TOYOTA\HV1\00 making sure to replace all the files that are there.
    3. Extract all files from to the following directory in your TECU 3 installation: ECU\TOYOTA\EFI\00

Connecting to an ECU on your vehicleEdit

NHW10 actually has a few different computer ECUs inside. It is only possible to read information from one of them at any one time. Here is how to connect to a specific ECU:

  1. TECU Main Screen

    Main Screen of TECU3

    Connect the OBD plug of the VAG COM adapter to the OBD port in your car. This port is located on right hand side, underneath the steering wheel of your car.
  2. Launch TECU 3 software.
  3. ​Press Ctrl+M on the main screen
  4. Select "TOYOTA" and press Enter
  5. You will then be presented with a number of different computer ECUs which you can connect to. The following ECUs are relevant to NHW10:
  • ​ABSv0 - ABS system in the car
  • EFIv0 - Internal Combustion Engine computer
  • HVv1 - Inverter computer
  • HVBATv1 - High Voltage battery computer
  • SRSv0 - Supplementary Restraint System
Click to select an ECU and press Enter

To switch to anoher ECU, press Ctrl+E on on the main screen of TECU.

Reading ​Diagnostic Trouble Codes (DTCs)Edit

  1. Press Ctrl+D on the main TECU screen to see any errors recorded against the ECU that you have currently selected
  2. If you wish to clear the error codes, press Ctrl+D again.

You may like to refer here for more detailed explanation of some of the error codes:

and here:

Reading Real time ParametersEdit

  1. TECU Parameters

    TECU3 Parameters Screen

    Press Ctrl+T on the main TECU screen to see real time parameters from your selected ECU.
  2. TECU will communicate with your vehicle and eventually load up values for all available parameters. This may take some time.
  3. Press Ctrl+S at any time on the parameter screen to save these to e a TXT file. This file will be saved in the LOG directory of your TECU folder.
  4. Press Ctrl+E to start recording a CSV file of all the parameters. Press Ctrl+E again to stop. The CSV fille also be placed in the LOG directory of TECU. Please note that if you want to look at these CSV files in Excel, you will need to first open the CSV file in Notepad and replace all ';' with ',' and save the file. The file will then open in Excel.

Peforming ActionsEdit

Actions are performed on the Parameter screen (Ctrl+T) in the main TECU screen.

Adjusting Battery State of Charge

  1. Connect to the car, using procedure described above.

  2. Press Ctrl+E on the main TECU screen and select item 11 - HVBAT Version 2 and press Enter or the button with the picture of a checkered flag.
  3. Press Ctrl+T on the main TECU screen.
  4. Select the "Rewrite SOC" action from a drop down on the bottom of the parameter window.
  5. Type 10 into the text box next to the drop down.
  6. Press Enter or double-click on the text box.
  7. The battery indicator on the MFD display of the car will drop down empty and the car will start charging the battery.

Performing Special Functions Edit

Re-initialising the battery computer Edit

TECU allows you to re-initialise the battery computer, thereby wiping all the data the battery computer (HVBAT) stores about the the capacities of your battery sticks. It is a very good idea to perform this function if new or replacement cells are added to the battery pack.

Here is how to perform batter computer re-initialisation:

  1. Connect to the car, using procedure described above.
  2. Press Ctrl+E on the main TECU screen and select item 11 - HVBAT Version 2 and press Enter or the button with the picture of a checkered flag.
  3. Press Ctrl+I on the main TECU screen to launch InfoECU tool.
  4. Press Ctrl+O or the refresh button and wait for Info InfoECU to complete. When done, it will print out various information about the HV battery ECU in your car.
  5. Press ESC to exit.
  6. Press Ctrl+F to open special functions screen and choose the first item - Re-initialise the battery computer and press Enter or the button with the picture of a checkered flag.
  7. A modal dialog will pop-up asking to connect to the car, turn the car ON but not to start the engine, making sure that "READY" indicator on the dash of the car is OFF.
  8. Press the left button on the bottom of the dialog, to continue. A counter will begin, wait for it to finish.
  9. Another dialog will pop-up asking you to turn the dash off, leaving the Accessory on.
  10. Press the left button on the bottom of the dialog, to continue. Another counter will being, wait for it to finish.
  11. Another dialog will pop-up asking you to turn on the engine.
  12. Press the left button once the engine is started, to continue. Another countdown will begin while TECU is issuing the wipe instruction, wait for it to finish.
  13. In the last dialog a green message should appear which informs you that the procedure is complete. Press ESC to complete and return to the main screen.

After re-initialization, the car will cycle charge the battery a few times and you may experience a few "turtles" and the performance will be poor until the computer re-adjusts.