Converting from OBD0 to OBD2 is a modification many car enthusiasts consider for various reasons, often related to engine swaps or accessing more advanced diagnostic capabilities. However, a common misconception is that this conversion is as simple as swapping out parts and plugging in a new harness. This is far from the truth, especially when it comes to the wiring harness.
One of the first points to understand is the fundamental difference between OBD0 and OBD2 systems. OBD0 (On-Board Diagnostics generation 0) is an earlier, less standardized system, while OBD2 (On-Board Diagnostics generation 2) is a more advanced and standardized system mandated in later vehicles. This difference extends deeply into the vehicle’s electronics and, crucially, the wiring harness.
The idea that an OBD2 harness will simply plug into an OBD0 system is incorrect. OBD2 harnesses are designed with different connectors and wiring configurations that are not compatible with the plugs in an OBD0 car. Attempting a direct plug-and-play approach will not work and can potentially damage your vehicle’s electrical system.
For a successful Obd0 To Obd2 Conversion, particularly when dealing with engine management systems (EMS), retaining the original OBD0 engine harness is generally the recommended and most practical approach. The reason is straightforward: your OBD0 car’s chassis and cabin harness are designed to interface with the OBD0 engine harness. These connections are specific to the vehicle’s year and model.
While some might consider swapping the entire harness – engine and cabin – to an OBD2 version, this introduces a significant level of complexity. It’s not merely a matter of unplugging one harness and plugging in another. An OBD2 cabin harness is designed for a vehicle with an OBD2 system throughout, meaning it will likely have different connectors, wiring routes, and integration points with other vehicle systems compared to your OBD0 car.
Attempting to use a complete OBD2 harness in an OBD0 car often results in a “rat’s nest” of cut and spliced wires, requiring extensive custom wiring and potentially introducing reliability issues down the line. Unless you are undertaking a highly specialized build, such as a K-swap which often necessitates different wiring strategies, modifying and adapting your existing OBD0 harness to work with the OBD2 components is usually the more efficient and less headache-inducing path.
In conclusion, when planning an OBD0 to OBD2 conversion, especially concerning engine management, understand that it’s not a plug-and-play harness swap. Retaining and adapting your original OBD0 harness is generally the most sensible strategy to avoid significant wiring complexities and ensure a more reliable outcome. Careful research and a solid understanding of automotive wiring are essential for a successful conversion.
