You may have noticed that the new MS3Pro Mini connector bears a striking resemblance to the connector on your older Microsquirt unit. This similarity is not coincidental; it’s intentional. You’re correct in thinking that you can repin your current harness connector, replace the Microsquirt, and install the MS3Pro Mini as an upgrade.

Here’s a guide on how to proceed, along with some helpful tips and tricks:

    1. You CANNOT import a Microsquirt tune into a MS3Pro Mini (MS2 vs MS3), since the firmware is entirely different.
    2. You CAN however export/import individual tables, settings, etc. to give yourself a leg up
  • IF USING ALED and/or WLED:
    1. As additional Spark Outputs with pull-up resistors
      • You can remove those pullups as the Mini has 4x REAL logic level outputs, reference the pinout guide below
    2. As Programmable Outputs
      • You CANNOT wire them to the Mini’s Spark Outputs
      • Instead, wire them to Spare Injector Outputs, reference the pinout guide below
    1. Crank/Cam Sensor Wiring (Opto, Hall, VR, etc.):
      • Crank Sensor to the CKP +/-
      • Cam Sensor to the CMP +/-
    2. If your Hall or Optical Sensor requires pull-up resistors:
      • If you soldered a pull-up inside the Microsquirt – use the internal pull-up DIP switches inside the Mini ECU
      • If you have a pull-up in your wiring – you can leave it alone OR use the pull-up DIP switch
    3. If your VR Sensor requires a shunt:
      • If you soldered a VR shunt inside the Microsquirt – use the internal shunt DIP switches inside the Mini ECU
      • If you have a shunt in your wiring – you can leave it alone OR use the shunt DIP switch
    4. If you have a fuel-only application triggering off Coil Negative:
  • TachOut ABILITY
    1. Mini does NOT have a dedicated TachOut pin
    2. Instead, one of the internal Mini DIP switches is a 12v Pull-Up for Injector H
      • To drive a 12v tach, wire it to Injector H and Switch ON the TACH P/U DIP Switch
    1. Mini has an on-board 4-Bar MAP Sensor (and an on-board 1-bar Baro Sensor)
    2. You can wire your existing external MAP sensor to one of the 4 available Analog Inputs
    3. MAF and O2 are no longer dedicated inputs, and can be used as Analog Inputs
    1. Any unused Injector Outputs can be repurposed as Generic Programmable Outputs

Repinning your Microsquirt Harness

We have a handy, super low cost wiring harness upgrade kit to help you adapt your Microsquirt harness to work with MS3Pro Mini.
Once you have the above items planned out, see the below video for how to de-pin the Microsquirt connector using the below table to re-pin it for your new MS3Pro Mini!

Video: https://www.youtube.com/watch?v=uXTkm_XV2OY&t=147s