Bosch PW IAC on 1101 box install questions | AEM
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suprant0010
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Joined: 11/13/2014 - 09:15
Bosch PW IAC on 1101 box install questions

Hi guys, I'm running an aem 1101 box for a Supra. I'm trying to ditch my stock stepper iac which has been nothing but problems for a Bosch 3 wire iac I picked up from the junkyard, and I had a few questions.

I was vaguely told I had to put a diode on the wires going to it, the details were left out so I started researching it. Basically what I've gathered from the megasquirt guys is I need the banded side of the diode connected to the 12v+ leg and the other to the ground, they call it a "flyback diode". What I haven't been able to find is what kind of diode specifically and why its needed in the first place?

Next question is about which pin im supposed to use for pw output. Reading through the pinout, I see pin 20a is labled pw1, but then 29b is labled pw1outi, not sure which is the real pw1.

Lastly, about the settings, I havent't found a setting that actually turns the PW function on, does it just come on when I turn the stepper function off? Or is there something else I have to enable? 

AEM_NS
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Joined: 06/06/2014 - 09:31
The 3 wire IAC's are unique

The 3 wire IAC's are unique in that they require two PWM input signals - a regular one and one that's the inverted "mirror" image.  This functionality isn't supported by the 1101 EMS thus I suggest finding and using a 2 wire PWM IAC.  If you use a PW pin (PW1 or PW2) for the IAC, it'll already have a flyback diode on it.

suprant0010
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Joined: 11/13/2014 - 09:15
Thanks for the response, so

Thanks for the response, so if the diode is built in, the person telling me to put one must have been misinformed.

I was actually going to follow someone elses setup to make the 3 wire work on 1 pw output.  They used a 50w resistor to keep 1 leg partially energized all the time,  then ems would control the other. Running a 2 wire is no problem either, I could get one if this  method is unsuccessful.