Many car owners assume that having an OBD2 port in their vehicle means it’s fully OBD2 compliant and compatible with any standard OBD2 scanner. However, some owners of older General Motors vehicles, particularly around the 1994 and 1995 model years, have discovered a frustrating issue: their OBD2 port doesn’t seem to work with typical OBD2 scanners. This situation can be particularly perplexing for those trying to diagnose car problems themselves.
One owner of a 1995 GMC Sonoma experienced this firsthand. Despite the presence of an OBD2 port, multiple “over the counter” OBD2 scanners failed to communicate with the vehicle’s computer. These scanners would power on when connected to the port, indicating a functional connection, but no data could be read. Even a Craftsman scanner with a display showing protocol attempts couldn’t establish communication.
Upon contacting tech support for the Craftsman scanner, the owner learned of a known issue with certain 1994 and 1995 GM vehicles. These vehicles were manufactured with OBD1 computer systems but were equipped with OBD2 style diagnostic ports. This mismatch creates an incompatibility with standard OBD2 scanners, which are designed to communicate with OBD2 computers. A mechanic friend confirmed this suspicion, noting that his professional-grade SnapOn scanner was able to connect and read data, likely due to its ability to automatically detect and adjust to different protocols.
Further investigation revealed that the emissions sticker on the GMC Sonoma did not actually include the OBD2 certification marking, adding another layer of confusion. The owner’s initial assumption, like many others, was that an OBD2 port automatically meant an OBD2 system.
Frustrated by this discovery, the owner considered a DIY solution: creating a hybrid cable using OBD2 and OBD1 connectors, along with the correct pinout diagrams, to connect to an OBD1 compatible scanner. Alternatively, finding a scanner specifically designed to handle this type of GM hybrid system could be another option.
This situation raises questions about the broader implications of such design choices. Forcing owners to rely on expensive dealership scanners or specialized equipment to diagnose their vehicles can be seen as a significant inconvenience. It limits the ability for DIY repairs and potentially drives business towards dealerships, which have the advanced tools to overcome these manufacturer-created obstacles. Whether this was an intentional design flaw or a result of parts shortages during manufacturing, the outcome is the same: frustration and added expense for vehicle owners trying to maintain and repair their Chevy or GMC vehicles from this era.
