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Old 03-16-2013, 06:20 PM   #1
jrbamc
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2000 Ford Focus DOHC... another IAC question

Ok, so I've replaced the IAC and many of the other sensors that are the usual suspects concerning idle issues with the Zetec, and all was good for a few months. Now that it's time to get the emissions and tag it is showing a CEL again, P1504. The wires to the IAC look ok, maybe I do need another IAC, even though I cleaned it really good last weekend. My car had the engine replaced a few year ago with another, but I am not sure now what year the motor actually is. Is there a stamped serial number somewhere that would tell me? I ask because I see different IAC valve images when searching the web, and maybe there are different part numbers for the IAC for different year engines? Are there specific IAC's for each model year Zetec DOHC from 2000 thru 2004, and what are the associated Ford part numbers? I need to get this CEL cleared by the end of March. Are the various IAC's interchangeable? They all look different inside and out! Many thanks!


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Old 03-16-2013, 08:24 PM   #2
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IAC valves for 2000 - 2004 Zetec engined cars should all be the same; they may not look identical but they will all be functionally equivalent. It's a solenoid operated valve and its outward appearance and dimensions aren't that critical except where it mates up to the intake manifold. (Perhaps also you're seeing pictures of ones fitted to later Duratec or even SPI engined cars.) Also don't trust "stock" or generic images used to illustrate parts on web sites.

Delphi, Airtex and Motorcraft all make that part. Ford part # is F7RZ-9F715-AB

Your DTC code is fairly specific and, while the IACV may look clean, the code is indicating an electrical fault. It may be internal.

P1504 - Idle Air Control (IAC) Circuit Malfunction
This DTC is set when the PCM detects an electrical load failure on the IAC output circuit.
Causes:
IAC circuit open
VPWR to IAC solenoid open
IAC circuit short to PWR
IAC circuit short to GND
Damaged IAC valve
Damaged PCM
The IAC solenoid resistance is from 6 to 13 ohms.
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Old 03-17-2013, 08:38 PM   #3
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Question

Thanks for the response... here is a little more. Now I know some of you have gone over this a zillion times... IAC issue continues. Went to a local pull-a-part and unbolted a few IAC's. Getting good at this no-look IAC removal and install procedure.
Anyways, my 200X Focus intake manifold has the little "-O-O" grooves where the IAC mounts, with the little gasket that fits into there. So then, some intake manifolds have a flat gasket that fits between the manifold and the IAC. So are BOTH needed, does having both cause a problem, is either preferable, what year intake manifold has the groove and which do not? Endless choices, what is the answer for each year, all, or none?
I mounted one of these junkyard IAC's (after cleaning it well) and used both gaskets and seated the valve well, and still, 5 minutes after start up the dang CEL came on with P1504 again. Yes I am going to break down and buy a brand new one. I just need a day or two of no CEL to get my emission test passed and my tag before March 31. If the brand dang new IAC pops a code then how to check the wires? They look ok and the IAC end looks undamaged, so how would I check/test/verify each of these items:

IAC circuit open - where?
VPWR to IAC solenoid open - VPWR?
IAC circuit short to PWR - where?
IAC circuit short to GND - where?
Damaged IAC valve - (I know, get a new one.)
Damaged PCM - PCM? If bad then why does car even run?

Inquiring minds want to know.

Oh, the Conley GA Pull-A-Part had over a dozen recently aquired 200X Foci, lots of good stuff, so I fixed a few other little issues with my car while I was working on this problem. Just in case some of you are local Fanatics.
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Old 03-17-2013, 10:31 PM   #4
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The IAC circuit is pretty straightforward as it's a linear electromagnetic solenoid so it needs power and a ground. The IACV has two wires going to it - black/yellow and green/yellow. Black/yellow is ground; green/yellow is power. Black/yellow goes to pin 63 of the PCM. Green/yellow ends up at the fuse box and is the source of 12V power. I believe the position of the plunger within the solenoid is varied by turning the ground on or off (similar to how the fuel pump/fuel pressure is controlled.) But I'm not positive.

So...

"IAC circuit open - where? -- Ford speak for any disconnected wire in the circuit. Start checking wiring continuity with a multimeter at each end of the harness. Have you checked the PCM connector for corrosion?
VPWR to IAC solenoid open - VPWR? - no 12V power source; check fuses, wiring, the usual.
IAC circuit short to PWR - where? - 12V power not going where it's supposed to; possibly shorted within the valve itself. Check wiring continuity.
IAC circuit short to GND - where? - same as above
Damaged IAC valve - (I know, get a new one.)
Damaged PCM - PCM? If bad then why does car even run? - Remote - as in teeny tiny possiblity - PCM circuit that controls that function is somehow damaged or failed. A Ford catch-all for any electronic trouble. "

Since you swapped a couple of valves over and they're all throwing the same code - which you cleared each time, right? - then I'd say the problem is in the harness or connectors (especially after major surgery like an engine swap).
But measure this: "The IAC solenoid resistance is from 6 to 13 ohms" anyway.
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Old 03-17-2013, 11:43 PM   #5
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Thanks for clearing up a few things. Maybe the IAC's are ok.

Is there a fuse that handles only the IAC circuit?

Where would the PCM be located? (I can probably Google that.)

The engine swap was a couple of years ago, ran fine, no issues.
The IAC problems started August/Sept 2012. Had what I thought were serious transmission issues that went away upon replacing the TPS. The idle issues continued and then went away for a few months after finally buying a new IAC, and then they came back about a month ago.

Can I use MAF cleaner on the other electrical connections?

So there should be a black/yellow and a green/yellow at the fat end of the harness? I assume there is a big plug there, so I could check continuity from that end to the IAC plug end... if I had a meter. (Trip to Wal-Mart.)

Or... with the battery disconnected and the fat end unplugged (??) I could meter those two wires ends and should get a reading (send a signal out to the IAC and back again)?

I get the concept but can't visualize the in-hand part.

Thank you for your continued attention.
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Old 03-18-2013, 12:00 AM   #6
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If I had an IAC and an ohm/multimeter meter in hand is it correct to say that by touching the probe ends to the two metal contacts inside the IAC connector plug I should be able to verify if the circuit is good or bad inside the IAC?
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Old 03-18-2013, 09:57 AM   #7
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So if I were to do this:

Disconnect neg term @ batt
Disconnect plug at IAC and pull plug up into view.
Plug in 12v test light or Multimeter leads into the IAC plug metal contacts.
Reconnect neg batt term.
Turn key...

I should at some point see the light come on or 12v on the meter IF the IAC circuit is good from batt pos to the IAC plug through the test device back to IAC plug to ground, right? Yes/No?

If no light on or no voltage on meter than the IAC circuit is broken somewhere in the harness.

Last edited by jrbamc; 03-18-2013 at 09:59 AM. Reason: Another thought
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Old 03-18-2013, 01:06 PM   #8
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So I went to Wally World and got a volt/ohm meter. I checked the IAC I took off my car using info at this link:

http://www.autozone.com/autozone/rep...96b43f802e8154

The IAC passed that test. (Either the IAC is OK or I'm doing it wrong.) So did the other three IAC's from the junkyard, whatever that means.

So how do I check the wires from the IAC plug on the pigtail to... wherever they go?
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Old 03-18-2013, 10:16 PM   #9
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Quote:
Originally Posted by jrbamc View Post
Is there a fuse that handles only the IAC circuit?
No.

Quote:
Originally Posted by jrbamc View Post
Where would the PCM be located? (I can probably Google that.)
Behind the passenger side lower kick panel.

Quote:
Originally Posted by jrbamc View Post
Can I use MAF cleaner on the other electrical connections?
Any mild solvent should do.

Quote:
Originally Posted by jrbamc View Post
So there should be a black/yellow and a green/yellow at the fat end of the harness?
Black/yellow only. Green/yellow goes directly to power source (i.e. fuse box) in this case, iirc.

Quote:
Originally Posted by jrbamc View Post
Or... with the battery disconnected and the fat end unplugged (??) I could meter those two wires ends and should get a reading (send a signal out to the IAC and back again)?
Kind of. Just connect each end of the black/yellow wire to your multimeter and ensure there is continuity from the unplugged connector pin 69 to the relevant IACV plug prong. Resistance in ohms for a continuous circuit should be close to zero. An open circuit will read infinite or "open" (duh).

The circuit for VPWR is more complicated. There are a couple of splices in the circuit because several other items are powered by that lead going back to the fuse box. You need a wiring diagram and need to confirm continuity section by section. pm if you want a wring schematic.

I think your last two posts are addressed by the above. Your test procedure is theoretically OK; multiple IACVs testing good points to a harness wiring fault. Most faults are at or near connectors or splices or are where wiring has been previously moved/bent/twisted.
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Old 03-18-2013, 10:27 PM   #10
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Oops. Correction; that's PCM connector pin 83 for the IACV.
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