The 1990 Chevy Silverado utilizes the 12-terminal ALDL (Assembly Line Diagnostic Link) connector, often mistakenly referred to as OBD1. While true OBD1 was implemented in some 1994 and 1995 California emissions vehicles, the 1990 Silverado uses a GM-specific ALDL system. So, if you’re looking to use a modern OBD2 reader on your 90 Silverado, you’ll need to understand the differences and how to bridge the gap. This article explores using a Tech 2 scan tool with your truck and alternatives for pre-OBD2 vehicles.
Understanding the Difference Between ALDL and OBD2
The key difference lies in the communication protocols and connectors. ALDL uses a proprietary GM protocol and a 12-pin connector, while OBD2 utilizes standardized protocols (e.g., ISO 9141-2, SAE J1850) and a 16-pin connector. This standardization allows a single OBD2 scanner to work across various makes and models.
Using a Tech 2 on a 1990 Chevy Silverado
While designed for later model GM vehicles, a Tech 2 scan tool with the appropriate software (e.g., GM NAO 33.004) can communicate with a 1990 Silverado. This software version supposedly covers vehicles from 1991 to 2013. However, older software versions might offer more comprehensive diagnostic capabilities for mid-1990s vehicles. The Tech 2 requires a Linear Flash Card to store the software.
Alternatives for Pre-OBD2 Diagnostics
For vehicles like the 1990 Silverado, alternative diagnostic solutions are available:
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Snap-on MT2500: This “brick” style scanner offers bi-directional control, similar to the older Tech 1A, providing more in-depth diagnostic and testing capabilities than simple code readers.
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Laptop-Based Solutions: Using a laptop with an ALDL interface (like the 1320 electronics ALDL) and software like TunerPro or WinALDL can offer diagnostic functionality. However, these solutions often lack bi-directional control found in the Tech 2 or MT2500.
The 1995 Transition: ALDL with an OBD2 Connector
Interestingly, 1995 marked a transitional year. GM vehicles, including the 1995 Corvette and trucks, started using the 16-pin SAE J1962 connector (the same as OBD2). However, these vehicles still employed the ALDL protocol, essentially using the OBD2 connector as an ALDL connector. This change was primarily driven by California’s OBD I regulations, paving the way for the federal OBD II mandate.
Conclusion
Diagnosing a 1990 Chevy Silverado requires understanding the nuances of the ALDL system. While a Tech 2 with the correct software can communicate with these vehicles, options like the Snap-on MT2500 or laptop-based solutions provide alternative diagnostic approaches. The shift to the 16-pin connector in 1995, while still using the ALDL protocol, highlights the evolution leading to the standardized OBD2 system we know today.
