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Thread: Wiring for AAC valve

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Posts: 1-7 of 7
2015-05-10 13:29:21
Wiring for AAC valve
Started investigating why my cold idle won't hold. Found the issue to be that the ACC valve is non-operational. No matter what values I set the valve to in Nismotronic, the idle speed doesn't change.

-Checked the resistance on the AAC, 10.5Ohm, all good!
-Getting power +12V at one pin
-Other pin, GND is floating (I'm assuming the ECU controls this as a ground switched PWM output 0-100%?)
-Fuse 20 "Electronics B" is fine, it should be tied to the AAC according to the diagrams.

Help, why doesn't my ECU output any signal to the ACC? What should I check?
2015-05-15 11:59:59
Okay so here’s the wiring diagrams on the AAC valve, and how to troubleshoot it. First verify that you get +12V on one if the pins at the AAC with the key on.

If you get +12V on one pin, and no ground on the other, you have a wire break somewhere from the ECU connector E222 and connector F7
So where are these connectors located? Here’s the wiring diagram for the harness coming from the firewall

And here’s the diagram for the engine.

Now I’m all set for tonights troubleshooting session
2015-05-15 12:51:57
The engine harness is actually two sections. Once section for the starter and the body, the other for sensors/ miscellaneous crap. Where the two tie together is behind the motor. I have a spare harness laying around I'll post some pics of so you can get an idea of what you are looking for.
2015-05-15 16:14:00
I just had this problem but It was a power issue on the e206 plug I believe. You are having opposite problem. I'd start by checking continuity between AAC and e222 and then f7 to the ECU pin for AAC. that will narrow your search.
2015-05-15 17:22:45
I just did a quick test between the AAC and e222, no broken wire there.

Then I set the minimum AAC duty cycle to 95%, and tested the f7 pin. No signal

Could be a broken wire, or a fried ECU output. Will continue investigating tomorrow night when I'm at a proper garage.
2015-05-15 19:44:10
Do a continuity test from the ECU pin for AAC control and f7 pin. That will eliminate broken wiring.
2015-05-16 10:54:50
After doing what Lynx said, I know that there is continuity between the ECU pin and f7 pin. This leads to a faulty ECU

Does pin 113 correspond to AAC valve on every ECU? Just a few months ago I frickin replaced my EUDM ECU (Where the AAC functioned), to this USDM ECU:

A12 001 B57 is the ECU number

Will I need to change ECU one more time?
Last edited by Dala on 2015-05-16 at 10-56-33.
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