APEXi S-AFC Installation by Robert Pina


RED - Ignition Power

GREEN - RPM signal

BROWN - Ground Wire closer to ECU

BLACK - Ground Wire farther from ECU than brown wire

YELLOW - Air Flow Signal wire going to ECU

WHITE - Air Flow Signal from AFM/Pressure Sensor

BLUE - Optional voltage input (o2 sensor mod)

celicaECUlocation.jpg (74953 bytes)


ST165AFCpinouts.jpg (59348 bytes) ST185AFCpinouts.jpg (75726 bytes) ST205AFCpinouts.jpg (72915 bytes)
ST165 ST185 ST205

Now that you have all of the information, lets go over some key things to keep in mind during the installation. This assumes you have the documentation that came with the unit. If anyone has the OX pinout for ST185 and ST205 please email me at robert@alltrac.net

  • Splice the wires in according the pinouts above.

  • The Air Flow wire from the harness to the ECU must be cut.

  • The white wire goes to the wire coming from the engine bay.

  • The yellow wire goes to the wire going to the ECU.

  • The black and brown wires must be wired away from each other.

  • On my installation I used RPM signal #1.

  • Once installed turn the key on and check operation.

  • For cylinders choose 4.

  • For throttle choose the arrow pointing up.

  • For sensor type choose flap, in and out 2.

  • Start the car and troubleshoot.

O2 Sensor Mod

By connecting the blue SAFC wire to the OX pinout on your ECU you will be able to read o2 sensor voltage. This can be wonderful for more accurate display of your o2 sensor reading. Typically on a generic A/F gauge the lights are lit up for every 10th of a volt. Example: If your o2 sensor voltage was .82, .80, or .86 it would always light up the same light. Not until you hit .90 volt would the next light be lit up. Yet on the S-AFC the voltage is displayed up to 1/1000th of a volt. So you will get .812 voltage for example. This type of display is hard to read but can provide valuable information. To see the o2 sensor voltage go to the sensor check screen under input 2. The voltage will bounce around when off throttle, but will give you some good information under higher throttle loads.

Pictures provided by www.apexi-usa.com