HSD-4 wire colors

The red wires should all be grouped together and connected to a single fuse to 12 volt switched power. The fuse should be rated for the total current draw of all outputs being used, up to a maximum of 30 amps.

ECU connections

The inputs need a ground signal to trigger their outputs. Here are what outputs you can use to trigger the HSD-4 high side driver with DIYAutoTune engine or transmission management.

MS3-Pro: High current, PWM, injector, or tach outputs

MSPNP Gen 2: Output 1, output 2, boost, or tach outputs

MicroSquirt (transmission control): Shift solenoid, TCC, or EPC outputs

MicroSquirt (engine control): ALED, WLED, FIDLE, or tach outputs

MS3X: Mid current, tach, or injector outputs

MS1 or MS2: Relay control outputs or FIDLE (MS2 only)

GPIO board: General purpose, PWM, or high current outputs