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Circuit identification

posted Apr 23, 2016 15:27:43 by CharlesAcosta
I just finished section three. I was looking at a IAC solenoid wiring diagram and I noticed that the power and ground both go to the PCM. For instance one is labeled VPWR which is then spliced to different directions and the other is labeled IAC SOL. Ground sided switched?
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3 replies
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Tyler said Apr 23, 2016 19:49:09
Just for our reference, what vehicle were you looking at? Kinda wanted to look up the same diagram.

If I'm understanding you correctly, then yeah, I think you've correctly ID'd the motor as ground side switched. I think the power side actually comes from a fuse, and that fuse also happens to provide power to the PCM. Make sense?

The circuit you're describing sounds to me like a typical Ford PCM Power Relay setup. Here's a diagram I grabbed off an '02 F-150. Is this similar?

[Last edited Apr 23, 2016 19:49:19]
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CharlesAcosta said Apr 24, 2016 00:51:22
It's a 99 Mercury mountaineer 5.0. Yes you are right. The fuse powers the PCM which in turn the PCM power relay gets its feed from another fuse then branches out to different components. Does the VPWR labeled in the PCM has its own feed internally or is it only the power relay that supplies it? Thanks.
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Tyler said Apr 24, 2016 16:48:56
No problem! The VPWR wire at the PCM is solely a power input, possibly as a hot-at-all-times keep alive memory fuse.

The diagrams can get confusing at times, especially when it seems like one fuse powers half the car, lol.
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