For enthusiasts and mechanics working with Japanese Domestic Market (JDM) Toyota vehicles, accessing engine diagnostics can sometimes present unique challenges. While modern vehicles largely adhere to OBD2 standards, some JDM Toyota ECUs utilize the ISO14230-4 (5 baud init) protocol, which isn’t universally supported by all OBD2 scanners and applications. This article breaks down how to successfully connect to your JDM Toyota ECU using OBD2, focusing on the often-overlooked ISO14230-4 protocol.
It’s important to note that while some OBD2 Android applications struggle with this protocol, solutions do exist. Moreover, not every Bluetooth OBD2 dongle is equipped to handle ISO14230-4. Personal testing has confirmed successful connections with this setup on the following non-OBD1 JDM ECUs:
- ST215 3S-GTE A/T (89661-21330)
- ZZT231 2ZZ-GE M/T (89666-20060)
OBD2 Port Considerations for JDM Engine Swaps
Engine swaps, especially when incorporating JDM engines into vehicles originally intended for different markets, might necessitate the creation of an OBD2 port. However, in some cases, like the ZZT231 Celica, the North American OBD2 port is already compatible in terms of wiring, even if the OBD2 protocol used in North America differed. The key is to ensure the correct pinout.
The standard OBD2 port pinout for this application is as follows:
- SIL: Connects to the corresponding pin on the engine ECU. This pin assignment will vary depending on the specific ECU model. Consult your ECU wiring diagrams for precise identification.
- Pin 4 & 5: Ground connections. In some instances, these grounds may need to be directly connected to the ECU grounds to resolve connectivity issues.
- B+: 12V power supply for the OBD2 tool. It’s generally advisable to avoid constant power to this pin to prevent potential battery drain when the tool is not in use.
For successful communication, an ELM327 Bluetooth dongle is recommended. The BAFX PRODUCTS OBDII Diagnostic Interface has been tested and confirmed to work reliably. While other ELM327 dongles may function, compatibility can vary. If you possess alternative models, testing them beforehand is a prudent step before purchasing a new one.
Image: BAFX Products OBDII Bluetooth Diagnostic Interface, a recommended ELM327 dongle for JDM OBD2 connections.
Utilizing Car Gauge Lite for JDM OBD2 Diagnostics
While not the most visually refined application, Car Gauge Lite has proven effective in establishing communication over the ISO14230-4 protocol during testing with JDM Toyota ECUs.
Image: Car Gauge Lite application icon, a functional Android app for JDM OBD2 diagnostics.
Before launching Car Gauge Lite, ensure your OBDII Bluetooth device is paired within your Android device’s Bluetooth settings.
The initial screen of Car Gauge Lite is shown below. Be aware that the free “Lite” version is supported by intrusive advertisements, which can hinder efficient use. A paid, ad-free version is available and recommended for regular or professional use. It is advisable to confirm connectivity with the Lite version before purchasing the paid upgrade.
Image: Car Gauge Lite main interface, highlighting the initial dashboard view.
A crucial step for successful Jdm Obd2 communication within Car Gauge Lite is enabling a specific preference setting.
Image: Car Gauge Lite preferences menu, showing the necessary setting for JDM OBD2 compatibility.
With this setting enabled, and the ELM327 dongle connected to your vehicle’s OBD2 port and the ignition turned to “ON” or the engine running, you can proceed to establish a Bluetooth connection within the app.
You will encounter up to four dialog boxes prompting for selections. Remember that your OBD2 Bluetooth adapter’s MAC address will differ from the one shown in examples. Locate your device’s MAC address within your Android Bluetooth settings and note it for the connection process.
Image: Car Gauge Lite Bluetooth connection dialog, the first step in pairing with your OBD2 adapter.
Image: Car Gauge Lite Bluetooth connection dialog, a subsequent step in the OBD2 adapter pairing process.
Successful ECU Connection!
Upon completing these steps, Car Gauge Lite should successfully establish a connection with your JDM ECU, granting access to diagnostic data.
Image: Car Gauge Lite dashboard after successful JDM ECU connection, displaying real-time vehicle data.
Like most contemporary OBDII Android applications, Car Gauge Lite allows for extensive customization of your dashboard. You can tailor the displayed fields to monitor the specific parameters relevant to your needs and vehicle. This personalization is key to making the diagnostic information readily accessible and useful.
