For automotive enthusiasts and professionals working with older vehicles, particularly those equipped with early Electronic Control Modules (ECMs), the need for reliable diagnostic tools is paramount. Accessing and interpreting data from these systems often requires specialized interfaces. Previously, connecting to an 8192 baud ECM for diagnostic purposes could be cumbersome, involving serial adapters and complex circuitry. However, a simpler and more efficient solution is now readily available: a USB ALDL cable built around the FT232RL USB-to-Serial module.
Traditional methods often involved Parallax 28030 units or similar serial-to-USB adapters. These setups typically necessitated converting the TTL level signals of the 8192 baud ALDL (Assembly Line Diagnostic Link) to serial using a MAX232 circuit, and then converting that serial signal to USB. Building a MAX232 circuit on proto boards can be a tedious process, not to mention the challenges of soldering connections to a DB9 connector. This complexity added time and potential points of failure to the diagnostic process.
The introduction of the FT232RL USB-to-Serial module offers a breath of fresh air for DIY diagnostic cable construction. This module streamlines the process significantly. By utilizing this convenient piece of hardware, connecting to an 8192 baud ECM becomes remarkably straightforward, requiring only two wires. No external resistors, ICs, or diodes are needed, simplifying the wiring to just two essential connections. This simplicity is a major advantage, especially for those who appreciate homebrew hardware solutions where ease of assembly is highly valued.
Testing this FT232RL based cable on a vehicle confirms its effectiveness. It establishes a reliable connection and successfully passes diagnostic tests, such as the TunerPro “test for cable” when disconnected from the car, a feature not always consistent with other cable types.
Constructing this USB ALDL cable is also cost-effective. Assuming access to a male ALDL connector or even just utilizing bare pins, the build process involves only a few quick solder joints. Encasing the module in a simple project box further enhances its durability and professional appearance. The total cost for a functional USB ALDL cable, including the FT232RL module with its integrated USB cable and a project box, can be remarkably low, potentially under $12. Adding a male OBD1 connector can create a polished, professional-grade cable suitable for regular use or even resale.
The FT232RL module ensures both simplicity and quality. Its reputation for reliability suggests a long lifespan for the constructed cable. While testing has been successfully conducted at 8192 baud, further investigation into 160 baud compatibility could be explored for broader application across different ECM types. This simple, efficient, and affordable USB ALDL cable represents a significant improvement over older, more complex methods, making OBD1 diagnostics more accessible and user-friendly.
