[Izzy46]

Thanks DStage, I did as you suggested and the IAC works well. The idle butterfly turned out to be reversed so it was a bit of a surprise the first time I started her up.

Any way, I'm going back to my old thread with the next set of challenges.

[DStage]

The reversal was sort of expected since your circuits with transistor is essentially an inverter. ETC IAC input is proportional to PWM so higher duty cycle meaning more positive state equals larger opening angle of the throttle valve. Most likely you also had it set so by default in your tune. But once you put the signal through inverter the higher duty you had at microcontroler output the lower it got at the ECU output and IAC input to ETC. Sometimes those things are easier to be checked in practice though

[PSIG]

To clarify the options for solution, what you did was retain the Speeduino IdleOut circuit intact, adding a 5V pullup. The advantage to this is simplification, using the existing outputs and wiring connections of Speeduino. It results in a proper 0V-5V square-wave to the ETC as required, although it is inverted. Invert the operation in TunerStudio.

The alternative is to take the output directly from Mega D5, by disconnecting R47 from Q5 pin 2, and sending that signal from R47 to the ETC idle pin. The D5 output is already 0V-5V, and not inverted. However, to get the signal out of the Speeduino board into the wiring harness either requires removing other IdleOut components, or simply not installing them if building the Speeduino board with ETC in-mind.

I hope that makes sense, and highlights ETC is similar to any other component you use. What does the signal have to look like for the component to operate properly, and how do you configure Speeduino and its circuits to provide that? Rock on!