OBD1 B-series Wiring Guide

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OBD1 B-series Wiring Guide​

Wiring an OBD1 VTEC B-series into a 92-95 Civic​

The most common cars for swaps are the EG-chassis line of Civics. Since there were way more base models produced than EX/Si models, chances are that your car is not already wired for a VTEC swap. Here's a quick chart of what to check when wiring in your 94-95 Integra B18C1 or 94-95 del Sol VTEC B16A3 into your EG. Most jdm motors will also follow this guide, but some changes will be made to your stock harness for it to work properly. Ensure that the following are all hooked up before you get any deeper into trying to figure out what's wrong.

The B16A/P30 as well as the B18C5 if using an obd1 electronics setup will need 6 wires while the B18C1/P72 and H22A/P13 will need 7 wires (additional wire for IAB control).

PartWire ColorPinoutNotes
VTEC SolenoidYellow/GreenA4
VTEC Oil Pressure SensorBlueD6
VTEC GroundBlackChassis Ground
Knock SensorRed/BlueD3
EVAP Purge PowerYellow/Black12v power
EVAP Purge SolenoidRedA20
Secondary Intake Solenoid (IAB)Pink/BlueA17P72 and P13 ECU only for B18C1 and H22 intake manifolds

If you have an EX/Si/VX most of these are already ran. Also, it has been our experience that most 1992 Civics, regardless of the trim level, are all wired for VTEC already. When doing a GSR swap, all that needs to be run is the knock sensor and the IAB's. For the rest of the model years, and the lower trims, you will need to run all of these wires. The professional way to do this is to actually re-pin the harness connector on the passenger side shock tower to accept these new wires and re-pin the ECU connector harness as well. Re-pinning tools are fairly inexpensive and can be found at most electronics stores. This way, you can simply plug in your obd1 GSR or del Sol VTEC motor with its harness right into your car. it retains the stock look, and makes your swap look much more professional than simply duct taping wiring together. It is also a good idea to wrap the new wires in loom much like the stock harness parts are.

VTEC Wiring​

If you are running a p28/p30, this applies to you. It may work on other OBD1 ECU/engine setups as well, but i'm not promising anything. Directly from the solenoid you will need to run the green/white wire to pin A4 on the ECU, which is the VTEC Spool Solenoid Valve Control. Next, connect the orange/blue wire to pin D6, which is the VTEC oil pressure switch input. Finally, the black wire from the VTEC pressure switch must be grounded. If you are running a USDM p30, make sure you wire up your knock sensor to pin location D3, otherwise VTEC will not engage.

IAB Wiring​

In order to make the Intake Air Bypass Solenoid activate when you swap a B18C1 into your civic/del sol you need to connect 2 wires. Coming from the solenoid there will be a yellow/black wire and a pink/blue wire. The yellow/black wire goes to the main pgm-fi relay and will see 12 volts constantly when the key is on. The pink/blue wire is what the ECU grounds to activate the solenoid and goes to pin A17.

If you are using an ODB2 GSR engine or intake manifold, note that the polarity was revered. See obd2 b18c1 into a 5th gen civic for more details on changing A20 over to A17.

Adding an Air/Fuel Gauge​

Most of your typical A/F gauges will come with three wires. My autometer one had a red wire, a black one and a purple one. The red and black are self explanatory, just make sure the red goes to a 12v source that gets power only when the key is on. You can find one in the fuse box using a test light very easily. Ground the black wire. The purple wire will be the one that reads the O2 voltage. An O2 sensor sends a voltage between .0 volts and .5 volts to the ECU, we are going to splice into this and then your a/f gauge translates that into little colorful lights to make you extra cool. Splice your purple wire into the white wire going to ECU pin D14.

How to Check the Voltage on your Throttle Position Sensor​

After performing a swap, many times the throttle position sensor on the engine is broken, forcing you to use one from your old d15 or d16 (or whichever you pulled). The Honda TPS has three wires coming from it: green/white , a red/blue , yellow/white. Your primary focus will be on the red/blue wire, as this is the one that sends a voltage to the ECU telling it how open or closed your throttle is. The ECU expects .5 volts to be closed throttle and 4.5 volts to be Wide Open Throttle (WOT). The red/blue wire goes to pin D11 at the ECU. Rotating the TPS will change the voltage, when you take it off, you'll notice that the holes are slotted so it can move. If you are fortunate enough to have Hondata Datalogging or an Apexi V-AFC you can use their inbuilt functions to read the TPS voltage. If you do not have such a device, you can use a Voltmeter or similar device. Ground one lead on the chassis somewhere and use touch the (+) lead to the pin on the TPS (should be the center pin) and measure the voltage. Rotate it until it reads .5 volts, then tighten it down. Have a friend press the gas pedal to the floor and also check that WOT reads 4.5 volts.
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