How To Install a SAFC in a Honda Fit

How To Install a SAFC in a Honda Fit


The Honda Fit has revived the small hatchback in the Honda stable that seemed to be missing for so long after the demise of the Honda Civic SI (EP3). The Honda Fit has definitely become one of the hotter hatchbacks in the sport compact market, and you can see that the aftermarket following is coming along nicely.

The new 2015 Honda Fit is coming soon and we’re excited as anyone for the new Earth Dreams engines, but today we are working on a 2007 Honda Fit GD. Piggyback computers aren’t what they used to be, but that wont’ stop us from showing you How To Install a SAFC in a Honda Fit.


The Apexi Super Air Flow Converter is a electronic device that is wired into your existing ECU harness and intercepts the airflow signal or in this case the Manifold Absolute Pressure signal. The AFC computer is a piggyback device that is capable of adjusting fuel trims dependant on RPM or engine speed, and allows you to split the values into two separate tables for high or low throttle use.

Take out the SAFC 2 wiring harness and examine the wiring diagram below, this diagram shown is for vehicles equipped with a Manifold Absolute Pressure (MAP) sensor.


To access your Honda Fit ECU, you will need to open the passenger side door and adjust the seat as far back as possible. The ECU is mounted to the kick panel, and must be removed before you can begin wiring the SAFC in.

Kicking off the How To Install a SAFC in a Honda Fit guide, is the red power wire on the Apexi Super AFC harness. Before taking this wire and soldering it into your ECU harness however, you should disconnect the negative terminal on your battery to prevent any damage.


Once you have the battery disconnected, locate the first block of ECU wires which should be a 31 pin connector, we’ll call this connector A. Grab the RED SAFC wire which should be teed directly into PIN 3 of the A block 31 pin Honda Fit ECU harness.

Next, you will be wiring in the low reference or chassis ground for your Apexi Super AFC. Take the two SAFC wires BROWN and BLACK, and note the way that Apexi wants you to wire them in. Take the Honda Fit ground wire, which is PIN 5 on the 31 pin A connector, and tee the brown and black wires in correctly. Make sure to note the distance and that the orientation of the ground wires must be exact. Make sure that the brown wire is teed into the ground CLOSER to the ECU than the black wire.


This is the way you should have this ground wired, and it’s imperative you wire this in correctly. Improper wiring will lead to the piggyback unit being damaged, and Apexi will not warranty these damages.

Now it’s time for the throttle position sensor (TPS) signal, which represents the GRAY wire of your SAFC wiring harness. Tee this into PIN 15 of the 31 wire A ECU connector for the proper TPS signal. After you have wired in the gray throttle wire, you can elect to tee into the knocking signal of your Honda Fit. The Knocking (KNK) pin on your Honda Fit ECU harness is PIN 9 on the 31 pin A connector. If you wish to have the knocking signal displayed on your SAFC, wire the PURPLE AFC wire to this pin on your ECU harness.


It’s time for the first and only cut in this entire How To Install a SAFC in a Honda Fit Guide, and that’s the Manifold Absolute Pressure (MAP) wire. PIN 19 on the 31 wire A plug. Make sure to cut in a way that leaves enough space or slack on either end of the wire for you to work on. Solder the yellow wire of the SAFC harness to the ECU side, and the WHITE wire of the SAFC harness to the engine side of the ECU harness.

The last step in our How To Install a SAFC in a Honda Fit article is the Engine Speed wire, or the RPM wire. This wire is located on the D plug or the last plug on the ECU harness, this is comprised of 31 pins as well, so don’t get confused.


The RPM wire on your Honda Fit GD ECU is PIN 26 of the 31 pin connector D ECU plug, and it’s the bottom most pin shown in the diagram above. Once you have this last SAFC wire connected and wired in (GREEN SAFC WIRE) you are done with the installation of your Apexi Super AFC into your Honda Fit!

Have any questions about the install or wiring diagrams? Leave them below!

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