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P1506: Replaced IAC and no change

P

PurpleMystique

Hard-core CEG'er
Joined
Nov 16, 2004
Messages
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Location
Greater Des Moines Area
I'm getting a P1506 on my full '01 Taurus 3.0. I've had this CEL on and off since I had the engine installed. Typically, the idle sits around 1000 rpm. When I decelerate (neutral/clutch in), the idle sits at about 2000 until I come to a stop, at which point it drops down to 1000. Occasionally, it will drop to 1000 as I decelerate but jump back up to 2000 until I come to a stop.

I replaced the IAC but immediately got the same code. Do I need to use the 2.5 IAC? Will it even work? Thanks.
 
I am getting the same kind of error, plus one. P1504 IAC circuit fault and a P1506 IAC overspeed error are the ones I am getting with an 04 3L Taurus swap. I asked in this thread:
http://www.contour.org/ceg-vb/showthread.php?t=37199

I tried changing out the IAC with another 3L one but the problem did not change. I can't figure it out and I haven't had a chance to throw a 2.5L IAC on yet.
 
Oh right, I'm not paying enough attention. I was thinking I had a vacuum leak, but now I am starting to think that might be the case (since I have a code that you do not), but also there is something in the tune that is looking for the 2.5L voltage from the IAC and the 3.0L is different so it's throwing a code. I am new to 3Ls so I am not the most informed person on this topic.
 
I got a mail-order tune from NPG, I'd hope that if this is just a setting in the tune that can be corrected, that they would have done it, but it's entirely possible that it was missed.
 
Did you disconnect your battery for at least 5 mins to reset the PCM? I read that these cars have an adaptive PCM and adjust conditions to account for engine wear. So when you replace a part like this one, it has to adjust and relearn it. Also, I had an issue similar to this but it happened to be a bad TPS. Replaced and the issue came back and later I found I had a short in my tps harness which was easily fixed, problem solved.
 
I reset the PCM with my Xcal2 a couple of time for different things, but nothing has changed. There probably is a short but I am too busy right now to check it.
 
Some of the causes for this code are:
1) Engine vacuum leak
2) EVAP system problem
3) IAC circuit shorted to ground
4) IAC valve stuck open, or damaged
5) Throttle body or plate contaminated or very dirty.
 
Tony2005 said:
Some of the causes for this code are:
1) Engine vacuum leak
2) EVAP system problem
3) IAC circuit shorted to ground
4) IAC valve stuck open, or damaged
5) Throttle body or plate contaminated or very dirty.
Click to expand...

I know 4 and 5 aren't the case, and I'm pretty sure that 3 wouldn't be the case since it works well all the time. I have no idea about 2 and I just went through all of the vacuum lines last week, so I'm pretty sure 1 isn't it, but I wouldn't be cocky enough to say it's not possible.
 
I had as shorting IAC wire, so don't rule that out yet. With the key on, engine off- using a multimeter, connect the negative lead to the negative battery post and then probe the two pins on the IAC wire. Only one should have a voltage.
 
P1506 just says IAC overspeed which may not mean that the IAC is at fault. You already changed the IAC so... The description for this error is that the actual rpm 200rpm above target, closed loop IAC correction < .2lb min.
If the solenoid is electrically open or shorte the values would be P1504 or P0511.
So it seems you may have a vacuum leak or an evap system failure. Is the throttle plate closed all the way?
 
I have my TB optimized. I confirmed that the throttle plate closes and there's no light sneaking through around the edges, but I'm not sure how else to verify there aren't any air leaks.
 
I ran that test and got 12v on only one wire. ShoGoFast and I found a hose coming off the UIM right where the IAC bolts on that just had a bolt stuffed in it. We replaced the hose with a cap. I now just get the p1504, the p1506 is gone, but now I idle at 1500. Before I was at 1100. I can't figure this one out.
 
KAOS_2.5M said:
would any of the problems that cause a 1506 also cause a midrange miss?
Click to expand...
No.

[FONT=arial,verdana,helvetica,sans-serif]P1506[/FONT][FONT=arial,verdana,helvetica,sans-serif]
Idle Air Control Over Speed Error. [/FONT]
 
Tony2005 said:
No.

[FONT=arial,verdana,helvetica,sans-serif]P1506[/FONT][FONT=arial,verdana,helvetica,sans-serif]
Idle Air Control Over Speed Error. [/FONT]
Click to expand...

alright, thats what I was trying to figure out. I know 1506 was an iac overspeed code already. just didn't know if it could cause my problem
 
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