How To Install a VAFC2 in a Honda Civic

How To Install a VAFC2 in a Honda Civic


The VTEC Air Fuel Controller from Apexi Electronics is one of the best variable cam tuners on the market, and has been for a long time. When you are installing this piggyback computer into a VTEC equipped Honda, you can adjust the fuel trims, raise or lower the VTEC crossover point and much more. Today we’ll be installing a Apexi VAFC2 part number 401-A915, which is the first of the VAFC2 units to come black from the factory.

We’ll be showing you how to install a VAFC2 in a Honda Civic EX, this is a 1997 with the stock D16Y8 engine and a P2P ECU. To begin our how to install a VAFC2 in a Honda Civic, you will first be disconnecting the negative terminal on your battery.

To begin our How to, you will need to access your Honda Civic ECU which carries the P2P code in our 1997 Honda Civic EX VTEC. Open the passenger side door, and recline the passenger seat as far back as it will go.


The Honda P2P ECU is located behind the plastic kick panel shown above. Undo the small plastic pop rivet shown below.



Once this plastic pin has been unscrewed and removed, you can pull off the passenger side kick panel to expose your P2P Honda ECU.


Your Honda ECU is secured to the chassis by way of a bracket and two 10mm bolts. Remove these bolts to pull out the entire ECU and access the ECU harness and plugs.


Undo these 10mm bolts and the ECU should slide right out to you.


Note the orientation of the ECU and the ECU plugs as shown above, these are the wires you’ll be teeing into for our How To Install a VAFC2 in a Honda Civic article. Now go back to the VAFC2 manual and refer to the wiring diagram shown below for the proper installation diagram.


Before we begin our DIY guide, please take this time to review the proper way to “space” your wires as Apexi desires. The Apexi VAFC2 requires two kinds of these connections, where older VAFC and SAFC units required just one. Typically the ground wire is split into two wires that must be spaced, the newer VAFC2 requires two wires for power as well.



Let’s get things started with the two red power wires for your VAFC II, which should be teed into the 1GP wires on your P2P ECU. The switched power wire you are going to want is on the A plug, the 32 pin plug on the left hand side of the ECU facing towards you. The pin in question is the A11 plug, which is a yellow wire with BLACK stripe, and represents the 1GP1 switched voltage supplied by ECU.

Make sure to wire both red wires in succession, leaving a one inch gap between both points. Refer to the dual connection diagram above for a better idea on how they should be spaced and wired.

Now with the power connected, you’ll be doing the same for the ground wires which should be brown and black on your VAFCII harness. The ground wire on your P2P ECU is also located on the primary A ECU connector, and the pin in question is A9. The identification for this pin is LG1, which is the low reference signal sent by the ECU. This wire is brown with black stripe in it. Make sure to follow the exact instructions shown above, by teeing the brown VAFCII ground wire closer to your P2P Honda ECU.

With these four primary wires connected, you should now have power going to your VAFCII and it should be able to light up and work. Let’s take a look at the VAFCII wiring diagram to see what sensor wires are left that you must connect.


The VAFCII GREEN RPM wire is the next on our list, and this wire is the ICM or Ignition Control Module which feeds the tach signal to the ECU. Tee the green wire into the A20 wire on your primary A ECU harness.

The VTEC solenoid switch is the last wire on the A plug that you’ll need to connect. This wire is also located on the A plug and the wire is A8 which is the VTS VTEC Solenoid. This wire is the first you will be cutting into, make sure to leave enough slack on either end of the cuts. You are connecting the PURPLE VAFC II wire to the ECU side, and the YELLOW VAFC 2 wire to the ENGINE side. With this wire done, there’s just two more connections to knock out and those are on the D connector.

Automatic transmission equipped Civics are the only ones with the B plug in this year range, if you own a manual, do not be alarmed if you see a gap where the B plug should sit.


For ease of installation, unplug the D connector to finish up your VAFC2 installation. The next wire on your P2P ECU harness is the D3 wire, which is the manifold absolute pressure (MAP) wire. This wire is Red with a green stripe as you can see from the photo above.

Cut this wire in half much as you did the VTEC solenoid Switch wire in the previous step. This time the colors on the VAFC II harness are YELLOW to the ECU SIDE, and then the WHITE wire going to the ENGINE side of the MAP sensor wire.

And lastly the final wire in our How To Install a VAFC2 in a Honda Civic Guide is the throttle position sensor (TPS). This wire is D1 on your P2P ECU and is a red wire with a black stripe. Simply tee the 0-5 volt TPS wire in to your Apexi Super VAFCII and you are now done!

Good job! You have now completed our How To Install a VAFC2 in a Honda Civic article, if you need help setting up your VAFC, check here.