The following is a guide on how to convert your OBD0 Honda to a OBDI, with relative ease. To complete this converting your OBD0 to OBD1 article and take your performance vehicle to the next step, you will need the following parts :
- An obd1 distributor that matches your motor setup
- A distributor adapter allowing you to plug your new distributor up
- A obd1 ecu that will correctly run your motor setup
- An ecu adapter harness allowing you to plug in your new ecu.
- A four wire o2 sensor
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For our example, we will be converting a CRX Si w/B16A & OBD0 ECU to a P28 OBD1 ECU. Many times we get the question, ‘Why bother converting to OBD1?’ Well for most customers planning on an EEPROM flashing solution such as Uberdata, Chrome or Neptune, you will need an OBDI ecu to achieve this.
When you factor into the equation the cost of parts you will be selling once you complete the task, it really seems like a small price to pay for the ultimate ability to tune a vehicle. That makes converting your OBD0 to OBD1 well worth the modification dollars.
Distributor
You will need to replace your old distributor with an OBD1 version. Make sure you match the engine. For example, if you have a B-series VTEC engine, you’ll want a Del Sol, GSR, or Type R distributor. Others may work that I’m not familiar with, but I wasn’t going to risk it. If you have a D-series, then get one from a Civic. Just make sure it’s OBD1.
Now you will need to convert your existing harness to plug into this new OBDI distributor. You can do this one of two ways, either put OBD0 plugs on your new distributor, or put OBD1 plugs on your engine harness.
We prefer the second option, as that leaves your new distributor stock and resellable should you decide to go that route.
Engine Harness OBD1 Distributor
| Peach | White |
| White/Blue | White/Blue |
| Blue/Yellow | Blue/Yellow |
| Thin White | Peach |
| Peach/Blue | Peach/Blue |
| Blue/Green | Blue |
| Fat White | Yellow/Green |
The wires on the two pin connector had the same colors so I did not bother to list them above. Once the wiring is taken care of, simply bolt up the distributor (make sure the shaft is turned the proper way and isn’t 180 degrees off) and then plug it into the harness.
Oxygen Sensor
One of the differences between the OBD0 B16A and an OBD1 B-Series motors is the fact that you have to convert from two 1-wire oxygen sensors to one 4-wire oxygen sensor with heated wires. In order for the ECU to operate correctly, you will need to place the new sensor downstream from the original locations so that it can read all four cylinders. Normally there is additional wiring involved, because you have to add wires for the senor’s heater.
Conversion Harness
We really recommend the use of a Boomslang harness, as this will eliminate a ton of wiring hassle. When using such a flying loom, install of your new ecu is very straightforward, tidy and simple.
You will notice that there are several wires that are not hooked up. These wires include those for VTEC, Oxygen Sensor, CEL jumper, etc. I will not go into detail here because the instructions that are provided are very thorough and straight forward.
-Knock sensor goes to pinout D3 on the ecu
-Vtec pressure switch goes to pinout D6 on the ecu
-Vtec solenoid goes to pinout A4 on the ecu
-IAB (gsr B18C) goes to pinout A17
-O2 sensor heater control. One of the blacks on the o2 sensor go to pinout A6 at the ecu
-O2 sensor signal. White on the o2 sensor goes to pinout D14 on the ecu
-The other black on the sensor is a switched 12 volt. Splice into pinout A14
-Green or gray on the o2 sensor is the o2 ground. Splice into pinout D22
Enjoy your new OBDI vehicle!
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