ToyoDiag

ToyoDiag is a DIY diagnostic tool for older Toyota ECUs, especially the OBD1-era systems used from roughly the late 1980s through the 1990s.

It reads Toyota's TDCL / OBD1 serial diagnostic stream directly from the ECU and brings that live data to a PC over USB.

Main Features
  • USB PC data logging
  • Bluetooth support
  • Android app support
  • Error code reading
  • Set timing mode
Hardware
ToyoDiag DIY Toyota ECU diagnostic hardware
DIY ToyoDiag hardware for older Toyota ECUs.
What It Reads

It reads the same Toyota diagnostic data stream used by the original diagnostic tools, including RPM, coolant temperature, throttle position, manifold pressure, injector pulse width, vehicle speed, and ECU status flags.

All data can be read from a PC connected over USB, making it useful for troubleshooting, tuning checks, and general live monitoring on older Toyota systems.

Extra Functions

Bluetooth and Android

It also supports Bluetooth and an Android app with the same core functions as the PC software.

Workshop Functions

ToyoDiag can enter set timing mode, read stored error codes, and display them directly.