GCU Valve Test can be executed even if gearbox is out of the car with only GCU connected to the transmission.

This step will allow You to check if all valves inside the gearbox are OK.

Gearbox Valve Test:

a. TCU rewired according to manual provided by HTG
b. GCU connected to the gearbox
c. If the transmission setup is not yet installed in the car, Gearbox Valve Tester can be
utilized only while stable current supply is connected able to hold up 12-14v and 30A


  1. Tools required:
    a. Windows 10 64bit computer with internet connection
    b. External Datalogger: http://update.htg-tuning.com/datalogger-latest.zip
    c. Firmware Loader: https://update.htg-tuning.com/loader-latest.zip
  2. Connect GCU to computer via USB type-C Cable
  3. If GCU appears as not recognized device, download and install USB drivers:
  4. Open Firmware Loader (HTG-Loader.exe)
  5. In device list (1), Your GCU should be selected.
  6. Press “Connect” (2)
  7. If app froze, close it, and add HTG-Loader.exe to Your firewall exceptions.
  8. If GCU established connection to your computer successfully, Firmware list (3) fill update,
    and display all available firmware versions for your GCU.
  9. From Firmware list (3) select “test-valve.dec”.
  10. Press “Upload firmware”
  11. GCU will restart and will start upload process after a while.
  12. When progress bar (4) will reach 100%, GCU will restart again.
  13. Now, you may hear clicking noises from Your Gearbox – that is the sound that valves do.
  14. Open External Datalogger (HTG-DataLogger.exe).
  15. From the Device List (1) Your GCU should be selected.
  16. Press “Connect” (2)
  17. From the Datalogger channel section (3), select all channels.
  18. Press “Start” (4)
  19. Now in Data section (5), zoom out. On the Y axis You should have visible range from 0 to 3000. On the X axis (time, seconds) – for Your convenience.
  20. In the lower part of the chart (6) You will see signals coming out from GCU. In the upper part of the chart – signals from valve sensors.
  21. Control signals are odd channels (1, 2, 3 and so on), and sensor signals even (2, 4, 6…).
  22. Control signal 1 is responsible for sensor on channel 2, control signal 3 – for sensor 4, and so on.
  23. Now, check Your sensor signals. Only ONE sensor should rise at a time, and only when corresponding control signal is rising.If You see something like this:

    It means that more than one Valve is energized. In that situation problem was with wiring – wires were too thin.
    NOTE: If you see additional valve energized up to 10% – this is acceptable, and gearbox should work fine.

    In this example some valves are going in opposite direction. Here customer shorted channels
    2, 4, 6, 8 and 10 to the BAT+ in his TCU

    If Your chart looks ok – congratulations! Your power part of hardware is working correctly.
    You may proceed to calibrating Your device.
    If You spot issues in the log – check Your wiring and double check your TCU.
    If You cannot spot issues here – contact us, and we will help with troubleshooting!
    And if You have problems with interpreting the chart – just send us or community group picture of chart and You’ll find help 🙂