For enthusiasts of vintage vehicles and owners of OBD1-equipped cars, diagnosing engine issues can often feel like stepping back in time. While modern vehicles boast standardized OBD2 ports and readily available scan tools, the older OBD1 systems require a different approach. Commercial OBD1 scan tools can be expensive, often costing a significant amount. However, there’s a cost-effective and satisfying alternative: building your own Diy Obd1 Scan Tool. This guide will walk you through creating a fully functional OBD1 scan tool for under $10, utilizing readily available components and free software. This project not only saves you money but also provides a deeper understanding of your vehicle’s diagnostic system.
What You’ll Need to Build Your DIY OBD1 Scan Tool
Before we begin, gather the following components. The affordability and accessibility of these parts are key to this project’s budget-friendly nature:
- FT232RL USB to Serial Module: This is the core component that bridges the gap between your vehicle’s serial data and your computer’s USB port. You can easily find these modules online from various retailers. Look for options like the “Arduino FT232RL USB to Serial Module,” which are commonly available at a low price.
- Jumper Wires: These wires will be used to make the necessary connections on the FT232RL module. Dupont wires are a suitable and inexpensive choice.
- USB Cable: A standard USB cable (Type-A to Mini-USB or Micro-USB, depending on your FT232RL module) to connect the module to your laptop.
- Two Lead Insulated Wire: Speaker wire, phone line wire, or ethernet cable wire will work perfectly. You’ll need this to extend the connection from the module to your vehicle’s ALDL port.
- Electrical Tape (Optional): For insulating and securing wire connections.
- Basic Tools: Wire strippers, wire cutters, and optionally a soldering iron and solder for more permanent connections (though twisting and taping works for initial testing).
Step-by-Step Guide to Building Your DIY OBD1 Scan Tool
Now that you have all the necessary parts, let’s proceed with the construction of your DIY OBD1 scan tool. Follow these steps carefully to ensure proper assembly and functionality.
Step 1: Acquire the FT232RL USB to Serial Module
Purchase an FT232RL USB to Serial Module online. A search for “FT232RL USB to Serial Module Arduino” on platforms like eBay or Amazon should yield numerous affordable options. Ensure the module comes with jumper wires and a compatible USB cable if possible.
Image of the FT232RL USB to Serial Module as received, highlighting the included components.
Step 2: Prepare the FT232RL Module Wires
Upon receiving your module, it will likely come with pre-attached wires. For this project, we need to modify two of these wires. Cut two wires (for example, orange and brown as in the original guide) in half. Strip the insulation from both cut ends of one wire (orange) and one cut end of the other wire (brown). You will be using these prepared wire ends for the next connections. Set aside the remaining wires and wire halves, as they are not needed for this specific DIY OBD1 scan tool build.
Image showing the FT232RL module with two wires cut and stripped at the ends, ready for connection.
Step 3: Connect the RXD and TXD Pins and Ground
Locate the RXD and TXD pins on the FT232RL module. You will notice a jumper connecting these two pins. Remove this jumper. This jumper disconnects the internal loopback and allows for external communication. Take the two stripped ends of the same wire (the orange wires in our example) and connect one to the RXD pin and the other to the TXD pin. Next, take the stripped end of the other wire (brown wire) and connect it to the GND (ground) pin located on the module, typically in a corner.
Image illustrating the connection of wires to the RXD, TXD, and GND pins on the FT232RL module.
Step 4: Extend the Wires for ALDL Connection
Now, take your two-lead insulated wire (speaker wire, etc.). Connect both wires from the RXD and TXD pins together to one lead of your insulated wire. Connect the wire from the GND pin to the other lead of your insulated wire. This effectively combines the RXD and TXD signals onto a single wire for connection to the ALDL port and provides sufficient length to reach your vehicle’s diagnostic port. The length of this wire depends on your setup, but approximately 3 feet is generally sufficient. Mark the ground wire with tape for easy identification later.
Image showing the extended two-lead wire connected to the FT232RL module, with a marker on the ground wire.
Step 5: Computer Driver Installation and Module Test
Connect the USB cable to the FT232RL module and then to your computer. The red LED on the module should light up, indicating it’s receiving power. Your computer should ideally automatically recognize the module and install the necessary drivers.
Image of the FT232RL module connected to a laptop via USB, showing the power LED illuminated.
Check your computer’s device manager to confirm that the FT232RL module is recognized and installed correctly, usually listed under “Ports (COM & LPT).” Note the COM port number assigned to the module (e.g., COM3).
Screenshot of the Device Manager on Windows, highlighting the assigned COM port for the FT232RL USB to Serial Converter.
If the drivers do not install automatically, you may need to manually download and install the FT232RL USB driver for your operating system. A quick web search for “FT232RL USB driver download” will provide links to the necessary drivers.
Step 6: Connect to Your Vehicle’s ALDL Port and Run Diagnostic Software
Now, take your DIY OBD1 scan tool to your vehicle. Locate the ALDL (Assembly Line Diagnostic Link) port, typically found under the dashboard. Refer to an OBD1 pinout diagram to identify pin “M” (8192 baud data) and pin “A” (ground).
Diagram of the OBD1 ALDL port pinout, clearly indicating pin M (Data) and pin A (Ground).
Connect the wire from the RXD/TXD pins of your module to pin “M” on the ALDL port, and the ground wire from your module to pin “A”. For testing purposes, you can carefully insert the stripped wire ends into the connector pins, ensuring good contact. For a more permanent setup, consider using ALDL connector pins or a pigtail.
Image showing the ALDL port located under the dashboard of a vehicle.
Download and install free OBD1 diagnostic software like GMTDScanBasic from http://www.enghmotors.com/default.aspx. Follow the software’s instructions to configure the ALDL interface, selecting the COM port number you noted earlier. Connect to your vehicle through the software. If all connections are correct, the software should establish communication with your vehicle’s ECM (Engine Control Module).
Screenshot of GMTDScan software successfully connected to a vehicle, displaying diagnostic information.
You can now use the software to read diagnostic trouble codes, view live sensor data, and perform other diagnostic functions, effectively turning your laptop into a powerful OBD1 scan tool.
Screenshot of the GMTDScan dashboard interface showing live engine parameters and sensor readings.
Conclusion: Affordable OBD1 Diagnostics at Your Fingertips
Congratulations! You have successfully built your own DIY OBD1 scan tool for under $10. This project demonstrates that diagnosing and understanding your classic OBD1 vehicle doesn’t require expensive professional tools. By utilizing readily available and budget-friendly components, you can gain valuable insight into your vehicle’s engine performance and troubleshoot issues effectively.
With your new DIY OBD1 scan tool, you can now explore further diagnostic and tuning possibilities. Consider exploring software like TunerPro RT, a free tuning and data logging program, to delve deeper into your vehicle’s engine management system. This DIY approach not only saves you money but also empowers you with a greater understanding of automotive technology and diagnostics.
