My friend recently started a swap on his vx civic hatch and said he needed help with 02 wiring so i showed him this from hybrid automotive

Seven to Four Wire Conversion

The easiest approach to doing this conversion is to start with the correct four wire plug, and make the necessary connections to the existing seven wire oxygen sensor circuit & engine wire harness wires. This is the approach we employ as we find it to be the most straight foreword.


1 2
3 4
1-GRN/WHT 2-WHT
3-ORN/BLK 4-YEL/BLK




1 2 3 4
5 6 7 X
1-WHT 2-GRN/WHT 3-BLK 4-YEL/BLK
5-ORN 6-ORN/BLU 7-WHT/BLU


These diagrams represent the FEMALE wiring plug on the engine wire harness that the oxygen sensor plugs into. Cut the existing seven wire oxygen sensor off of the engine wire harness and connect the four wire oxygen sensor plug to the engine wire harness in the following way:

1 - Connect GRN/WHT on the four wire oxygen sensor plug to the GRN/WHT wire from the seven wire plug. (This is in wire location two on the seven wire plug.)

2 - Connect WHT wire on four wire oxygen sensor plug to the OAR/BLU wire from the seven wire plug. (This is in wire location six on the seven wire plug.)

3 - Connect OAR/BLK on the four wire oxygen sensor plug to the YEL/BLK wire from the seven wire plug. (This is in wire location four on the seven wire plug.)

4 - Connect YLW/BLK on the four wire oxygen sensor plug to the YLW/BLK wires that connect to the fuel injectors, IACV sensor, or EVAP Purge Control Solenoid Valve. All of these sensors/components share the same YLW/BLK circuit.



we are a little confused about the fourth wire any clarity on this we just dont want to screw something up

 

There has been a lot of talk about how to do this lately-- so time for a FAQ

Chances are, if you are even running yet, you are throwing code 41

first, get some basics as tought by pills: OBD1 Wiring Guides

now, here's what your dealing with....



First off, this is considering a b-series swap done using the VX harness.
a b-seires will not run off the 5-wire, mostly for the computer reasons. so, firs tthing to do is to pick up a 4-wire o2, found in just about every other civic besides the 1 or 2-wire equipeed ones.

now you have a 4-wire ecu, and a 5 wire harness. the easiest way to do this is to simply ignore the vx harness, and run the wires straight from the 4 wire plug up to the ecu. Use your own descresion as to how clean you want to make it, and re-pinning is also up to you.

here's what you need to do-

O2 Sensor Input - WHT to D14 (needs to be a shielded wire)
Heater Control - BLK to A6
Sensor Ground - GRN to D22
Sensor Voltage - BLK to A25 or B1 (both are 12-volt sources, so either works fine.)

again, note, this is for an obd1 vx with an obd1 ecu.
if you are using an obd2 ecu, check out our chart in the reference section to get the pinout locations.

or to use the harness wiring

a little more info--

Converting 1992-95 VX to 4 wire O2 using VX engine harness

All wires are present except for the power input, but all wiring can be done using the existing wires in the engine and cabin harness. The following wiring will trace the wires, color-coded, from the engine harness side of the shock tower plug to the O2 sensor you are wiring. Most all wires have color changes at each junction.

D14 - ORG/BLU at O2 plug (engine harness side) - WHT (4 wire O2 plug)
D22 - GRN/WHT at O2 plug (engine harness side) - GRN (4 wire O2 plug)
A6 - YEL/BLK at O2 plug (engine harness side) - BLK (4 wire O2 plug) There are 2 BLK wires and either one can make either connection. The second BLK wire needs to be connected at B1 or A25. The easiest thing to do is unpin D16 (BLU/GRN) at the ECU and tap it into B1 (YEL/BLK) or A25 (YEL/BLK). Then on the engine harness side O2 connector, connect the ORG wire to the BLK O2 wire.

 

Found this months ago never tried it ended up getting rid of the car before a swap

 

There is a guide somewhere, not sure if its on honda-tech but if you google it something will come up.

 

This diagram should help: