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IMRC stuck open by PCM

svtpimp

New CEG'er
Joined
Jan 26, 2007
Messages
20
Location
Ontario, Canada
Well I've had some trouble with my IMRC and have performed the transistor replacement twice. When it messed up with the 2nd transistor the IMRC would open and close, open and close, then just stopped working all together. So then I ordered a new IMRC from Ford, installed it, went for a test drive and it opened awesome once. After that it just stays open. So I pulled the wiring diagram at work and seen that there are 3 IMRC control wires comming from the pcm. Now the IMRC has power from the injector circuit and that was good, ground was good, so I figured that the IMRC control wires were ground swtiched by the pcm. So I measured the resistance from the IMRC plug to battery ground. The black/red wires had 0 resistance, where as the black/blue wire had a resistance of .946 ohms, therefor most likely grounded somewhere. So i pulled the UIM off to trace the wires through the harness to check for any worn through wires, none. Then I seen the connection on the left side of the intake manifold, checked resistance from IMRC plus to there, 0 for both wires. Checked it from the other side of the plug to the pcm harness, nothing. So then i plus it back into the pcm and check the whole circuit and its grounded again, even with the battery diconnected. Bad pcm? When I first start the car the IMRC is closed, then about 5-10sec later it opens and stays open.Any ideas? Sorry about the long post, any help would be great thanks Mike. BTW I hooked up the Snap On Modis and tried a KOEO/KEOR and it would just give me a 'test incomplete' and referred to the P1518 IMRC stuck open code. Thnaks in advance Mike.
 
Welcome :) . How many miles, what engine (2.5 or 3L-what 3L)? You may want to consider putting those info in your signature.

Check wiring harness for cracks or chaffed areas.
 
Sorry its a 1998 Contour SVT 2.5, 130 000km . Ive checked the whole harness, no rubbing or anything. No resisntance in harness from IMRC - PCM.
 
As you are aware, some causes for a P1518 are:
1) IMRC signal shorted to power ground (suspect)
2) IMRC signal shorted to return signal ground (suspect)
3) Transistor failure (you have ruled this out with a new IMRC)
4) PCM failure (suspect but wait until 1 and 2 has been ruled out).

Lets assume PCM is fine and wiring harness is the problem. At the PCM, during hot idle;
Pin 8 is Black/Blue wire and should have 5 Volts (IMRC)
Pin 42 - Black/Red wire ........12 v (IMRC)
Pin 24 - Black/Yellow .......< 0.1 v (power ground)
Pin 25 - Black/Red ...........< 0.1 v (power ground)
Pin 51 - Black/Yellow .......< 0.1 v (power ground)
Pin 71 - Green/Yellow ......12 - 14 v (vehicle power)
Pin 77 - Black/Yellow .......< 0.1 v (power ground)
Pin 90 - Yellow ..............4.9 -5.1 v (reference voltage)
Pin 91 - Brown ...............< 0.050 v (analog signal return)
Pin 97 - Green/Yellow .......12 - 14 v (vehicle power)
Pin 103 - Black/Yellow ......< 0.1 v (power ground)

Yes, I strongly suspect it is a wiring harness issue. If any of those wires do not check out, you should jumper them (end to end) and see if it checks out before changing the PCM. In any case, even if the PCM was toasted due a wiring harness issue, putting in a new PCM will only result in another toasted PCM unless you fix the harness issue. Check with Ford to see if you are covered under the Customer Satisfaction Extended Warranty.

Edit 99M03 Wiring Harness issue.
http://www.contour.org/FAQ/recall/99M03/
 
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Welcome to my nightmare! :laugh:

I've been through 3 IMRC's, swapped PCM, UIM/LIM rebuild, and oh yeah, a 3L.

I've had the same CEL code for almost 2 years now. In the spring, I'm replacing my main harness and injector harness to try and fix it finally. :rolleyes:
 
Thanks for the I was wondering if I was going to have to call ford to get the specs for all systems connecting to the IMRC. I will be testing all those wires on my next day off. Thanks Mike.
 
Is it detrimental to leave the IMRC Stuck Open?

I recently have had the same code thrown (although I haven't tried disconnecting the battery yet) along with a LEAN code which I'm guessing is caused by the IMRC being stuck open? (Please correct me if I'm wrong.)

2000 SVT owned since new with about 140,000 Miles. Only "mod" is a KKM Open Filter.

Sadly... I'm unemployed at the moment (well for 8 months) so I have to careful, but I was just wondering how bad it is to leave it that way for now.

Don't have the codes with me as I'm studying for a certification exam tomorrow, but if I need them for any help, I can try to get them when all is settled.

Thanks!
 
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