1-wire to 4-wire o2 conversion

We may earn a small commission from affiliate links and paid advertisements. Terms

If you bought a CX or DX civic with a 1-wire o2 sensor, you're going to have to convert to a 4-wire to run a b-seires ecu, and most of the "top of the line" d-series ecu's like the p28.

First things first, you need to physically buy a 4-wire o2 sensor. you can't send a heater signal to a device which has no heater circuitry and expect it to work :D

Wires on 4 wire O2:

WHITE: Signal Wire
GREEN: Signal Ground
2 BLACK: Both black wires are the heater circuit wires.

Using a P28 ECU (and should work for most obd1 ecu's with 4-wire controls)

Run O2 Sensor signal (white) To D14
Run O2 Sensor signal Ground (green) to D22 (or any good Ground)
Run O2 Sensor Heater Circuit Control (black) to A6
Run the other black heater circuit power wire to (A25) or any good switched +12VDC source.

(you may mix up the black wires... if car dies after it is warm/10-30 seconds, that's the first thing to swap over and troubleshoot.. theres no way to tell one from the other by looking at them)