For owners of the 97 Honda Prelude with the OBD2 USDM H22a4 engine, a common desire is to gain more control over engine timing and utilize aftermarket performance parts. One significant limitation of the OBD2 system in these Preludes is the ECU-controlled ignition timing, which prevents manual adjustments at the distributor. Furthermore, modifying the exhaust cam gear on H22a4 engines can trigger a CYP check engine light, hindering performance tuning. This is where converting to an OBD1 distributor becomes a valuable modification. While not directly related to “97 Honda Prelude Obd2 Jumper Pin 4 To Pin 5” in typical diagnostic procedures, understanding your OBD2 system is the first step in recognizing its limitations and exploring solutions like this distributor swap. Although “jumper pin 4 to pin 5” is often associated with grounding for diagnostic purposes in OBD2 systems, this modification addresses a more fundamental performance constraint.
Why Convert to an OBD1 Distributor?
The primary advantages of switching to an OBD1 distributor on your 97 Honda Prelude are twofold:
- Adjustable Base Timing: OBD1 distributors allow for manual adjustment of the base ignition timing. This is crucial for performance tuning, especially when you’ve made modifications like aftermarket camshafts or increased compression. Being able to physically rotate the distributor to adjust timing gives you a level of control that the stock OBD2 system simply doesn’t offer.
- Compatibility with Aftermarket Cam Gears: With an OBD1 distributor, you can freely adjust aftermarket exhaust cam gears without triggering the CYP (Cylinder Position Sensor) check engine light issue that plagues OBD2 H22a4 engines. This opens up a wider range of performance modifications and tuning possibilities for your Prelude.
Parts You Will Need for the Conversion
To perform this conversion, you’ll need the following components:
- OBD1 External Coil Distributor: Acquire an OBD1 distributor from a USDM H22a1 or H23a1 engine. These distributors have an 8-pin male connector, a key difference from the OBD2 distributor.
- 8-Pin Female Connector and Pins: You’ll need the female connector that mates with the OBD1 distributor. The best source for this is often a junkyard. Look for 92-95 Hondas, as they commonly used 8-pin distributor connectors. Cut the connector from the harness, leaving enough wire attached to facilitate soldering. Extract the pins from this connector as well.
- 4-Pin Male Connector and Pins: You’ll also need a 4-pin male connector. A readily available source for this is a 4-wire oxygen (O2) sensor pigtail, which can be found on many vehicles. Again, cut the connector with some wire and extract the pins.
Wiring the OBD2 to OBD1 Distributor
The core of this conversion lies in correctly wiring the OBD2 engine harness to the OBD1 distributor. The following wiring diagram outlines the connections:
| OBD2 Connector (4-Pin Male) | OBD1 Connector (8-Pin Female) | Function |
|---|---|---|
| Black | Blue/Yellow | CKP M (Crankshaft Position Sensor -) |
| Red | White/Blue | TDC M (Top Dead Center Sensor -) |
| White | White | CYP M (Cylinder Position Sensor -) |
| Yellow | Blue/Green | CKP P (Crankshaft Position Sensor +) |
| Green | Orange/Blue | TDC P (Top Dead Center Sensor +) |
| Blue | Orange | CYP P (Cylinder Position Sensor +) |
| Yellow/Green | Yellow/Green | ICM (Ignition Control Module) |
| Green | Green | ICM (Ignition Control Module) |
Wiring Steps:
- Locate the CKP Plug: Identify the Crankshaft Position Sensor (CKP) plug on your engine harness.
- Create the Harness: Using the 4-pin male connector (O2 sensor connector) and the 8-pin female connector (junkyard Honda connector), begin wiring based on the diagram above. Solder and heat shrink your connections for durability and weather resistance.
- Pin Connections: Carefully connect each wire from the OBD2 side to the corresponding wire on the OBD1 side according to the table. Double-check each connection to prevent wiring errors.
Important Considerations
- Accuracy is Key: Wiring mistakes can damage your ECU or distributor. Double and triple-check your wiring against the provided diagram before connecting everything. If you are unsure about your wiring skills, consult a professional mechanic.
- OBD2 Diagnostic Limitations: After this conversion, your distributor-related diagnostics will revert to OBD1 standards. While you gain timing control, you might lose some of the detailed distributor-specific diagnostic information available in OBD2. However, for performance enthusiasts, the trade-off is generally worthwhile.
- Professional Installation: If you are not comfortable with automotive electrical work, it is highly recommended to have this conversion performed by a qualified mechanic experienced with Honda vehicles and engine modifications.
Conclusion
Converting your 97 Honda Prelude’s distributor from OBD2 to OBD1 is a worthwhile modification for those seeking greater control over engine timing and wanting to maximize performance through aftermarket parts. By following this guide and carefully wiring the new distributor, you can unlock the tuning potential of your H22a4 engine. Remember to prioritize accuracy in wiring and consider professional help if you are not experienced with this type of modification.
