# OBD2 ABA throttle body



## Prof315 (Jan 5, 2009)

Well I can now confirm that an OBD2 ABA throttle body's built in IAC will work with MS3 and pretty darn well. BUT the duty values are far lower than I expected. I was running at 511Hz and with 1.7% DC idled at a steady 875rpm with 6* advance and ~15.2 to 1 AFRs. I suspect that bringing the advance up to 10* should get me to 925-950 with AFRs around 14.7.


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## MancusoGTI8v (May 24, 2002)

I am going to install a MS3X on a 1.8T.

I am planning on using this:










Can you help me with the pinout? 

Want to use TPS and idle control. I am assuming it is a PWM type idle control. Correct?

Thanks for the help.


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## Prof315 (Jan 5, 2009)

I have been meaning to update this.....
TPS pinout: Pin 4 is sensor ground. Pin 5 is sensor signal. Pin 7 is VREF (5V)

IAC pinout: Pin 1 is 12V Pin 2 is control (pwm)

Concerning the IAC portion of the throttle. It's weird..... although PWM control does work, it only works for me in open loop and I wound up wiring the valve backwards and using inverted control in MS. It _seems_ like the stupid thing is more like an electric temp door motor than a true pwm idle valve. That said I can still manage to idle the car steady at about 950 rpm with mine and it does catch the sudden increased engine load when I turn the air on pretty well.


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## MancusoGTI8v (May 24, 2002)

Thanks!

Will document my install and post back here.

Luis


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## the_mad_rabbit (Aug 10, 2003)

Prof315 said:


> I have been meaning to update this.....
> TPS pinout: Pin 4 is sensor ground. Pin 5 is sensor signal. Pin 7 is VREF (5V)




*AHEM* Back from the dead but... this is incorrect. Pin 7 is ground (brown/blue) that is incorporated into the main ground on the engine harness from T28
Pin 5 is indeed signal (red/bue) and pin 4 is VREF (5v) (red/white). You can switch them if you are making a harness from scratch but NOT if you are using a factory harness on the engine bay side and then using a pigtail connector that would normally go to the ECU/main wiring harness.

The IAC most likely will only work if you have power going to pin 3 (white/green, unknown voltage), and then power (unknown voltage)/ground to pin 1 and 2.

Cheers

-AJ


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## Prof315 (Jan 5, 2009)

the_mad_rabbit said:


> *AHEM* Back from the dead but... this is incorrect. Pin 7 is ground (brown/blue) that is incorporated into the main ground on the engine harness from T28
> Pin 5 is indeed signal (red/bue) and pin 4 is VREF (5v) (red/white). You can switch them if you are making a harness from scratch but NOT if you are using a factory harness on the engine bay side and then using a pigtail connector that would normally go to the ECU/main wiring harness.
> 
> The IAC most likely will only work if you have power going to pin 3 (white/green, unknown voltage), and then power (unknown voltage)/ground to pin 1 and 2.
> ...


Hate to tell you this but I have been running the OBD2 throttle body as I described in my Corrado with an MS3/3X and with an MS3Pro ( I upgraded) for nearly 3 years now without any real problems. I read TPS just fine and have acceptable control of the idle


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## the_mad_rabbit (Aug 10, 2003)

Prof315 said:


> Hate to tell you this but I have been running the OBD2 throttle body as I described in my Corrado with an MS3/3X and with an MS3Pro ( I upgraded) for nearly 3 years now without any real problems. I read TPS just fine and have acceptable control of the idle


Don't get me wrong, it will work if you aren't running a stock harness. If you switch them, you'll send power straight into the ground wiring that is part of the ground harness on the engine bay side. I have a similar setup with MS2 3.57 with an OBD1 TB. You can switch the wires, but only if you're not using the stock T28 harness. In my case, I am using a stock harness with the stock connector with Microsquirt.

-AJ


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## Prof315 (Jan 5, 2009)

the_mad_rabbit said:


> Don't get me wrong, it will work if you aren't running a stock harness. If you switch them, you'll send power straight into the ground wiring that is part of the ground harness on the engine bay side. I have a similar setup with MS2 3.57 with an OBD1 TB. You can switch the wires, but only if you're not using the stock T28 harness. In my case, I am using a stock harness with the stock connector with Microsquirt.
> 
> -AJ


And why would I even think about running a stock harness from that era? They are crap at 6-8 years never mind 20!


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## the_mad_rabbit (Aug 10, 2003)

Prof315 said:


> And why would I even think about running a stock harness from that era? They are crap at 6-8 years never mind 20!


Because mine was cherry out of a low mileage car that was stored in a garage  I built a full harness for my Jetta, but decided to try something different with my Corrado. And they really aren't all that bad... 
And, stock harness as in the engine side harness. Not the complete harness, lol.

-AJ


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## TheBurninator (Jan 7, 2009)

Just curious if anyone has gotten this to work with similar values on MS2?


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## The_Elusive_Pickle (Nov 7, 2014)

the_mad_rabbit said:


> *AHEM* Back from the dead but... this is incorrect. Pin 7 is ground (brown/blue) that is incorporated into the main ground on the engine harness from T28
> Pin 5 is indeed signal (red/bue) and pin 4 is VREF (5v) (red/white). You can switch them if you are making a harness from scratch but NOT if you are using a factory harness on the engine bay side and then using a pigtail connector that would normally go to the ECU/main wiring harness.
> 
> The IAC most likely will only work if you have power going to pin 3 (white/green, unknown voltage), and then power (unknown voltage)/ground to pin 1 and 2.
> ...


Sorry to bump the dead again but I am trying to get IAC on a stock 96 aba harness and have a few questions. What frequency did you run and what duty cycles? Also, I have 12V to pin 1, FIDLE at pin 2, and ground at pin 3 on the throttle body but I can't seem to find a frequency/duty cycle combo that actually adjusts my TPS in test mode like I would expect it to. Is that just not how it's supped to work or am I missing something.

Thanks
Joe


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## The_Elusive_Pickle (Nov 7, 2014)

The_Elusive_Pickle said:


> Sorry to bump the dead again but I am trying to get IAC on a stock 96 aba harness and have a few questions. What frequency did you run and what duty cycles? Also, I have 12V to pin 1, FIDLE at pin 2, and ground at pin 3 on the throttle body but I can't seem to find a frequency/duty cycle combo that actually adjusts my TPS in test mode like I would expect it to. Is that just not how it's supped to work or am I missing something.
> 
> Thanks
> Joe


To anyone finding this in the future, +12V to pin 1 and Idle to pin 2 is correct, there is just a difference between FIDLE and IDLE. IDLE is on MS3X and can handle the high frequency PWM needed for idle control by default whereas FIDLE doesn't seem to be able to. Also, leave Pin 3 open.


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## EURidahO (Jul 10, 2006)

The_Elusive_Pickle said:


> To anyone finding this in the future, +12V to pin 1 and Idle to pin 2 is correct, there is just a difference between FIDLE and IDLE. IDLE is on MS3X and can handle the high frequency PWM needed for idle control by default whereas FIDLE doesn't seem to be able to. Also, leave Pin 3 open.


One more graveyard bump.

Prof315 posted on the MSextra forums in 2015 saying that he ran it reversed. Signal to pin 1 and 12v to pin 2. Then run the valve inverted in the software.

I'm having issues with this valve with MS2 on a V3.57 board being really spikey with poor resolution. 15% dc won't keep the engine running, 16% idles at like 2k rpm.

What kind of frequency/DC values are you using?


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## The_Elusive_Pickle (Nov 7, 2014)

EURidahO said:


> One more graveyard bump.
> 
> Prof315 posted on the MSextra forums in 2015 saying that he ran it reversed. Signal to pin 1 and 12v to pin 2. Then run the valve inverted in the software.
> 
> ...


I never got the motor to idle well with the OBD2 throttle in closed loop so I went to open loop and just dealt with a fast idle (1100rpm ish) but I forget what the values were. If I remember correctly, playing with the frequency changed the DC ranges but mine were usually on the high side (like 50-60%). I have since swapped to an OBD1 setup, which is working pretty nicely (though I need to sort out A/C kick-up now that it's summer). For what it's worth, that runs from 40% to 70% with a 0.4 dashpot adder at 1021Hz in normal mode. The only real other tweak was setting a good the initial value table up instead of using last value. That helped alot with hunting. 

PWM is basically just a DC voltage control though, you could try throwing a resistor in line since you are running such low % anyhow. Might give you a little better resolution.


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## acee_dub (Jun 12, 2008)

I had all sorts of weird issues with setting mine up (MS2 v3 board), in the end cleaning the board and rebuilding the FIDLE circuit with all new components resolved it. Running the valve inverted as in Prof315's old threads, it works well around 180-250Hz on mine. Configured in open loop for now, may try going closed loop later but no need yet.

Testing using the JimStim really saves lots of time, if using the adapter provided by DIYAutoTune to power the JimStim, it will not have enough power for the idle valve motor to push open this throttle body against the springs. I just wired it to a car battery and jumped the JimStim's 12V & FIDLE pins into pins 1 & 2 of the throttle body connector, everything went fine for some quick tests. (Varying the coolant potentiometer opens the TB flap to the full range of about 24.5% TPS). 

Respect to need_a_VR6 and Prof315 for the help in that struggle


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## The_Elusive_Pickle (Nov 7, 2014)

acee_dub said:


> I had all sorts of weird issues with setting mine up (MS2 v3 board), in the end cleaning the board and rebuilding the FIDLE ...


I ended up swapping mine over to IDLE on the MS3X board and that helped me out too. FIDLE may just not quite be up to the task. I did have current draw issues when testing my OBD2 TB in general so maybe this shouldn't be surprising.


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