This guide provides a comprehensive Obd2 To Obd1 Jumper Harness Diagram, perfect for budget-conscious car enthusiasts undertaking DIY engine conversions. This wiring schematic, based on a P28 Uberdata conversion harness, outlines the connections needed to successfully integrate an OBD1 ECU into an OBD2a vehicle.
Understanding the OBD2 to OBD1 Conversion
Converting from OBD2 to OBD1 often involves using an adapter harness to bridge the gap between the different connector types and pin assignments. This diagram specifically details the wiring for Honda vehicles, utilizing a P28 ECU as an example. However, the principles apply to other OBD1 ECUs like the P30 and P72, with minor adjustments potentially necessary.
Detailed Wiring Diagram
The diagram below illustrates the pin connections between the OBD1 and OBD2 connectors. The left side represents the OBD1 connector pinout, while the right side represents the OBD2 connector.
A Connector:
- A1 to A4
- A2 to A1
- A3 to A3
- A4 to A8
- A5 to A2
- A6 to A6
- A7 to A16
- A8 – No Connection
- A9 to A12
- A10 – No Connection
- A11 – No Connection
- A12 to A27
- A13 to A18
- A14 – No Connection
- A15 to A17
- A16 to A19
- A17 to A26
- A18 – No Connection
- A19 – No Connection
- A20 to A15
- A21 to A20
- A22 – No Connection
- A23 to A10
- A24 to A23
- A25 to A11
- A26 to A9
B Connector:
- B1 to A24
- B2 to A22
- B3 – No Connection
- B4 – Blank
- B5 to C5
- B6 – Blank
- B7 to C29
- B8 to C16
- B9 to C6
- B10 to C18
- B11 to C4
- B12 to C14
- B13 to C3
- B14 to C13
- B15 to C2
- B16 to C12
D Connector:
- D1 to C10
- D2 to D5
- D3 to D6
- D4 to C7
- D5 – No Connection
- D6 to C15
- D7 to C8
- D8 – No Connection
- D9 to C17
- D10 to D16
- D11 to D1
- D12 – No Connection
- D13 to D2
- D14 to D7
- D15 to D8
- D16 – No Connection
- D17 to D3
- D18 – No Connection
- D19 to D4
- D20 to D10
- D21 to D12
- D22 to D11
Practical Tips for Harness Construction
When creating your jumper harness, consider using OBD2 connectors salvaged from an automatic transmission vehicle. Automatic transmission connectors typically have extra pins, providing a readily available source for replacing shorter pins on the OBD1 connector. This resourceful approach can further reduce the cost of your conversion.
Conclusion
This OBD2 to OBD1 jumper harness diagram offers a clear and concise guide for a successful DIY engine conversion. By carefully following the pin assignments and utilizing readily available resources, you can achieve a cost-effective and functional integration of an OBD1 ECU into your OBD2a vehicle. Remember to double-check all connections before starting your engine.
