Many car enthusiasts with OBD2B automatic transmission vehicles face a challenge when it comes to engine tuning. Often, the factory PCM (Powertrain Control Module) in these vehicles manages both the engine and the automatic transmission. This integrated system can complicate engine modifications and tuning, especially when aiming for significant performance gains. The solution? Utilizing an OBD1 ECU to take over engine management while retaining the factory OBD2 PCM for transmission control. This is made possible with a specialized dual adapter harness.
This guide explores how an OBD2B to OBD1 conversion harness can revolutionize your tuning capabilities for Obd2 Automatic vehicles, focusing on seamless integration and enhanced control.
Understanding the OBD2 Automatic Tuning Challenge
For vehicles equipped with OBD2B systems and automatic transmissions, the factory PCM typically handles both engine and transmission functions. While this integration is efficient for stock vehicles, it presents limitations when enthusiasts seek to enhance engine performance through aftermarket tuning solutions. Traditional OBD2 tuning methods can be restrictive, and for those wanting in-depth control over engine parameters, switching to an OBD1 ECU offers a significant advantage.
Introducing the OBD2B to OBD1 Automatic Transmission Harness
The dual adapter harness is engineered to bridge the gap between older OBD1 engine management systems and newer OBD2B automatic transmissions. It cleverly splits the signals from your vehicle’s wiring harness, directing engine control to an OBD1 ECU while ensuring the factory OBD2B PCM continues to manage the automatic transmission seamlessly.
This innovative approach allows you to install a standalone OBD1 ECU, such as the Hondata S300 AUTO ECU package, to precisely tune your engine for optimal performance. Simultaneously, your vehicle’s original OBD2 PCM remains in place, ensuring the automatic transmission operates as intended without disruption.
Key Benefits of Using an OBD2 to OBD1 Harness for Automatic Vehicles
- Enhanced Engine Tuning Capabilities: Unlock the full potential of your engine with the advanced tuning capabilities of OBD1 ECUs. Gain precise control over fuel delivery, ignition timing, and other critical engine parameters.
- Seamless Automatic Transmission Operation: Maintain factory automatic transmission functionality. The OBD2 PCM continues to control gear shifts, torque converter lockup, and other transmission-related functions without interruption.
- Simplified Installation: The harness is designed for relatively straightforward installation. It plugs directly into your factory ECU/PCM connectors, making the conversion process reversible and minimizing wiring modifications.
- Retain OBD2 Diagnostic Functionality (Transmission): Continue to use an OBD2 scan tool to diagnose any issues related to your automatic transmission through the factory OBD2 diagnostic port.
Important Considerations and Functionality Notes
- Check Engine Light (MIL) Behavior: With the harness installed, the check engine light will illuminate only for issues detected by the OBD1 ECU. Use the service check connector or your tuning system to read OBD1 ECU trouble codes.
- OBD2 PCM Codes: It’s normal for the factory OBD2 PCM to store some diagnostic trouble codes after harness installation. This is because certain signals are redirected to the OBD1 ECU. These codes are generally benign and do not affect the automatic transmission’s performance. OBD2 codes from the factory PCM will not illuminate the check engine light on the dash.
- OBD2 Scan Tool for Transmission Codes: To read any diagnostic codes from the factory OBD2 PCM (related to the transmission), you will need to use an OBD2 scan tool connected to the standard OBD2 port.
Compatibility
This OBD2B to OBD1 automatic transmission harness is confirmed to fit:
- 98-01 Honda CRV with automatic transmission. Overdrive functionality is preserved and operates correctly on 99-01 CRV models equipped with overdrive.
Required Components
To complete this conversion, you will need:
- OBD2B to OBD1 Automatic Transmission Harness (as described)
- OBD1 ECU Package, such as the OBD1 Hondata S300 AUTO ECU Package – specifically designed for automatic transmissions.
Installation Overview
Installing the harness is designed to be user-friendly:
- Disconnect and unplug your factory OBD2 PCM connectors.
- Connect the OBD2B harness connectors to the factory ECU/PCM plugs.
- Plug the OBD1 ECU connectors from the new harness into your OBD1 ECU.
- Connect the remaining OBD2 ECU plugs from the new harness back into your factory ECU/PCM.
For detailed installation instructions, always refer to the product manual provided with your harness.
Conclusion
Upgrading to an OBD1 ECU for your OBD2 automatic transmission vehicle using a conversion harness offers a significant leap in engine tuning capability without compromising the functionality of your automatic transmission. This solution provides enthusiasts with the best of both worlds: advanced engine management and seamless automatic transmission control, making it an ideal choice for performance upgrades and engine modifications.
