The world of car diagnostics and engine management has evolved significantly over the years. For car enthusiasts and those keen on monitoring their vehicle’s performance, understanding the On-Board Diagnostics (OBD) systems is crucial. If you own an older car equipped with OBD1, you might be wondering if it’s possible, or even beneficial, to convert to the more modern OBD2 system. This article delves into the complexities of converting an OBD1 car to OBD2, exploring the process, challenges, and alternative solutions to help you make an informed decision.
The question of converting OBD1 to OBD2 often arises from a desire to access more advanced diagnostic capabilities and utilize modern performance monitoring tools. OBD2 offers standardized diagnostic codes and a wider range of parameters that can be monitored compared to its predecessor, OBD1. For owners of pre-1996 vehicles (the year OBD2 became mandatory in the USA), the allure of OBD2’s enhanced features is understandable.
A user, hybridmomentspass, initiates a forum discussion about OBD1 to OBD2 conversion for their 1991 MR2, seeking enhanced car monitoring options.
Understanding OBD1 and OBD2
Before diving into the conversion process, it’s essential to understand the fundamental differences between OBD1 and OBD2.
OBD1 (On-Board Diagnostics Generation 1) was the early generation of automotive diagnostic systems. Implemented in vehicles before the mid-1990s, OBD1 systems were not standardized. This meant that each manufacturer had their own diagnostic connectors, communication protocols, and diagnostic trouble codes (DTCs). Accessing data from an OBD1 system often required specialized tools and manufacturer-specific knowledge.
OBD2 (On-Board Diagnostics Generation 2), standardized in 1996 in the United States, brought about a universal diagnostic system. OBD2 standardized the connector type (SAE J1962), communication protocols, and DTCs across all manufacturers. This standardization made it easier for mechanics and car owners to diagnose issues using generic OBD2 scanners. OBD2 also mandated more comprehensive emissions monitoring and reporting compared to OBD1.
Why Consider Converting to OBD2?
The primary motivations for considering an OBD1 to OBD2 conversion typically revolve around:
- Enhanced Diagnostic Capabilities: OBD2 systems offer more detailed diagnostic information, including a wider range of sensors and parameters that can be monitored. This can be beneficial for troubleshooting complex engine issues.
- Access to Modern Scan Tools: OBD2’s standardization means a wide array of affordable and user-friendly scan tools are readily available. These tools range from basic code readers to advanced diagnostic scanners and performance monitoring devices.
- Performance Monitoring and Data Logging: Many modern track day assistants and performance logging tools are designed to interface with OBD2 ports. These devices can log parameters like throttle position, brake input, RPM, and more, which are valuable for performance analysis and driver improvement.
ProDarwin suggests a standalone ECU as a potentially easier alternative for enhanced logging capabilities instead of OBD2 conversion.
The Complexity of OBD1 to OBD2 Conversion
While the benefits of OBD2 are clear, the process of converting an OBD1 car to OBD2 is far from straightforward and often more complex than initially anticipated. It’s not simply a matter of swapping a connector. A true OBD2 conversion involves replacing numerous components and systems, potentially including:
- Engine Control Unit (ECU): The OBD1 ECU is not designed to communicate using OBD2 protocols. You would need to replace it with an OBD2 compatible ECU.
- Wiring Harness: The entire engine and potentially chassis wiring harness may need to be replaced to accommodate the different sensors and ECU connections required for OBD2.
- Sensors: OBD2 systems typically utilize additional and different sensors compared to OBD1, such as downstream oxygen sensors, and sometimes different types of crankshaft or camshaft position sensors.
- Emissions Control Systems: OBD2 mandates more comprehensive emissions monitoring, which may require adding components like secondary air injection systems or different catalytic converters if your OBD1 car lacks them.
docwyte shares their experience of converting a VW Corrado to OBD2, highlighting the parts swapping involved, including wiring harness, ECU, and sensors.
Parts Needed for an OBD2 Conversion
If you’re determined to proceed with an OBD2 conversion, you’ll need to identify a compatible OBD2 system to transplant into your OBD1 car. Ideally, this would come from a later model of the same car or engine family that was originally offered with OBD2. For example, if you have a 1991 Toyota MR2 (as in the original forum post), you might consider sourcing parts from a 1996 or later Toyota Camry with the same engine, if an OBD2 version existed.
The key components you’ll likely need include:
- OBD2 ECU: Ensure it’s compatible with your engine and, ideally, from a mechanically similar engine.
- Engine Wiring Harness: The complete engine wiring harness from the OBD2 donor vehicle.
- OBD2 Sensors: All necessary sensors, including MAF sensor, oxygen sensors (upstream and downstream), crankshaft and camshaft position sensors, throttle position sensor, etc.
- OBD2 Diagnostic Port: The OBD2 connector and associated wiring.
- Potential Mechanical Modifications: Depending on the vehicle, you might encounter issues like different reluctor rings for sensors, different sensor mounting points, or even needing to adapt the intake manifold or throttle body.
codrus points out the extensive changes required for OBD2 conversion, including ECU, wiring harness, and potentially new sensors, using the Miata as an example.
Is OBD2 Conversion Worth the Effort?
For most car owners, converting an OBD1 car to OBD2 is generally not worth the time, cost, and complexity. The amount of work involved is significant, and the benefits are often outweighed by the availability of simpler and more cost-effective alternatives.
As many participants in the original forum thread pointed out, unless you have a very specific reason for needing a factory-like OBD2 system (perhaps for emissions compliance in a specific region, though this is rare), there are better ways to achieve enhanced diagnostics and data logging.
GameboyRMH emphasizes that basic OBD2 data logging might not be worth extensive effort due to potentially slow update frequencies, especially in older OBD2 systems.
Alternatives to OBD2 Conversion
Instead of tackling a full OBD2 conversion, consider these more practical alternatives to achieve your goals:
1. Standalone ECU
For performance enthusiasts and those seeking advanced data logging capabilities, installing a standalone ECU is often a superior solution. Standalone ECUs are aftermarket engine management systems that replace the factory ECU entirely.
Advantages of Standalone ECUs:
- Full Engine Control: Standalone ECUs offer complete control over engine parameters, allowing for custom tuning for performance modifications.
- Advanced Data Logging: Many standalone ECUs have built-in data logging features with high data rates, far exceeding the capabilities of basic OBD2 logging.
- Flexibility and Expandability: Standalone ECUs can often be expanded with additional sensors and features as needed.
- Simplified Installation (in some cases): While still requiring wiring and setup, standalone ECUs designed for specific engines can sometimes be installed more easily than grafting an entire OBD2 system.
Disadvantages of Standalone ECUs:
- Cost: Standalone ECUs can be more expensive than attempting an OBD2 conversion in terms of parts.
- Tuning Required: Standalone ECUs require professional tuning to run correctly and safely.
- Emissions Compliance: Standalone ECUs may not be emissions compliant, which could be a concern depending on your location and vehicle use.
MadScientistMatt suggests a race ECU as a plug-and-play option for MR2 Turbos seeking advanced data logging, highlighting standalone ECUs as a powerful alternative.
2. OBD1 Data Logging Solutions
If your primary goal is data logging and diagnostics without extensive modifications, exploring OBD1 data logging solutions is a smart approach. While OBD1 lacks the standardization of OBD2, there are still ways to access and interpret data from OBD1 systems.
Options for OBD1 Data Logging:
- OBD1 Scan Tools: Specialized OBD1 scan tools exist that can read data and trouble codes from older vehicles.
- DIY OBD1 Data Loggers: Projects like Arduino-based OBD1 to OBD2 translators or dedicated OBD1 data loggers are available for DIY enthusiasts. These often involve connecting to the diagnostic port and using software to interpret the data.
- ALDLdroid and Similar Apps: Apps like ALDLdroid are designed to interface with specific OBD1 systems using custom adapter cables and data definition files (ADX/ALDL files) to translate the data into readable parameters.
cgraner mentions Arduino-based OBD1 to OBD2 translators and apps like ALDLdroid as solutions for accessing OBD1 data without full conversion.
Conclusion: Weighing Your Options
Converting an OBD1 car to OBD2 is a technically challenging and labor-intensive undertaking. While possible in some cases, it’s often not the most practical or cost-effective solution for gaining modern diagnostic and data logging capabilities.
For most enthusiasts, opting for a standalone ECU or exploring OBD1 data logging solutions will provide a better balance of performance, features, and effort. Carefully consider your specific needs and goals before deciding if an OBD2 conversion is truly the right path for your OBD1 vehicle. In many cases, embracing the technology available for your car’s original system or upgrading to a performance-oriented standalone system will be a more rewarding approach.
