Vx 5-wire To 4-wire O2 Sensor Info

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If you did an OBD1 B18C or B16A swap into your 5th gen Civic VX, chances are you are throwing code 41 if you haven't converted the Oxygen sensor over to operate in the 4-wire way your ecu (like a p28, p30, or p72) is expecting.

If you have an automatic ECU, read this first: Convert a Honda ECU from Automatic to Manual


OBD B-series Swap into EG Civic VX
Civic EG VX harness used on B-series engine

A b-series will not run off the 5-wire, mostly for the computer reasons.

First, pick up a 4-wire o2, found in just about every other civic besides the 1 or 2-wire equipped ones. These can be found at the local auto parts store pretty cheap.

Now you have a 4-wire ecu and O2, but 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 discretion as to how clean you want to make it, and re-pinning the cannon plug is an option for a cleaner install.

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.)

If you are using an obd2 ecu, check out our ECU Pinouts in the reference section to get the pinout locations.
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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.


Thanks to b16vx for this info with pics :)

The VX 12v is pinned different than the P30/P28, so you need to repin it to the right point,

Remove ECU, then find D16 it is blu/grn

As you can see the plugs have a small hinge that allows better access to the pins.

Now you can cut it and add it to the right pin (B1 or A25) or if you are really good and have a pin lying around, just add them both to a new pin and reinsert it back into B1 or D25. I cut it, D16, stripped the end and inserted it into B1 (yel/blk)then taped the wires together to keep it from coming out,

Not the best pic, but you get the idea.

Once you have done the ECU part, keep the ECU disconnected and goto the bay, connect the correct wires together as described in the previous post. In my pic they don't look right, because the adapter wire I got to lengthen them was wrong, so I compensated at the o2 connection. Follow the color coordination above and you are set.

This highspeed little junction can be picked up at any electronics store, and is much easier and safer than twisting them together and taping them. Though if you have the equipment and the time soldering them is the best.

Then when you have made the connections, plug in the ECU and make sure the CEL is gone, if so electrical tape the harness up to keep it safe and good looking.

The last step is to test drive it and make sure that the CEL (or another) doesn't pop up.

Happy driving!!!
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Before we begin, here's a handy guide on how to remove wires from plugs correctly from our friends at FFSquad.


VX wiring guide for a B-series into a VX (OBD1)​

Locate the 6-pin cannon plug on the passenger side of the VX's shock tower.

The wires are in the following order:


Remove the following wires from the 6-pin VX plug.
Civic VX Cannon Plug 6.jpg

ORG/BLU - O2 Sensor
BLU/YEL - Knock Sensor

Now, locate the 10-pin cannon plug on the VX shock tower.

Civic VX Cannon Plug 10.jpg

The wires are in the following order:


Remove the rubber plug from the 2 unused sockets. Insert the ORG/BLU (O2 Sensor) wire into the socket between the BRN/BLK wire and the BLK/RED. (top row, center)

Next, If your B-series engine has a knock sensor and are using a p72 or p30 ecu, insert the BLU/YEL (Knock Sensor) wire into the socket next to the other BLU/YEL WIRE. (bottom row, right)

P28's won't look for or care about the knock sensor so you can skip this step if that is your ecu.

If you are installing a B18C1 or H22, you will also need to run the IAB control. Move the RED wire on your ecu harness from A20 TO A17 for your secondary runners on the intake manifold.

Finish up by plugging in your ecu in the footwell and the 3 remaining cannon plugs to the B-series harness.
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