ICM testing

[Teearohwhy]

I recently checked the resistence of my ICM as described in the tech info forum. I found one of the secondary windings to read 9.23ohm while the other two were around 6.3ohm. Does this mean I need to replace the oddball. I also noticed that it has already been replaced once as its appearance is slightly different from the other two. Any help would be much appreciated.

[justdave]

Teearohwhy [interesting surname or nickname? by-the-way], unfortunately, the info you provided in your post is in-exact. Also, the Techinfo tables of resistance values do not contain your 2003 year SLE within them. In the world of electronic devices, one must be very specific, as i am sure you will agree.
First, there is no procedure in Techinfo for checking the ICM (Ignition Control Module); your post concerns checking the resistance readings of your Ignition COILs.
Your post also states "9.23ohm" for a Secondary Winding resistance reading; we must assume that you inadvertantly left out the "K" before "ohm"...as no secondary windings should ever have such a low resistance of only 9.23ohm (again, precise info is required when dealing with electronics).
Now that we have addressed those issues, there are questions and potential answers we can give you.
IF you measured 9.23 K ohms (9,230 ohms) across the secondary winding of your newer/replaced-previously Ignition Coil, and measured 6.3 K ohms (6,300 ohms) across the secondary windings of your OEM/original Ignition Coils, those readings are in the ballpark, and your coils will 'work' OK.
However, as stated within the Techinfo post, mis-matched ignition coils 'can' produce unwanted symptoms including rough idle, and misfiring. (The PCM may or may not log those misfires into it's 'History' section of memory.) *When you think about the difficult task they must perform (many thousands of Volts of 'push', many times per second, in the high heat found in and near the engine) you can realize that "matched" ignition coils are the best thing to have.
Has your vehicle's PCM generated any DTCs?...turned the Check Engine or MIL light "on"?...or have you just been 'feeling' misfires and/or experiencing rough idle?
Perfection in the GM world is often un-obtainable, even if you were to replace ALL of your ignition coils with newer GM Parts (expensive). The ICM is also known to be a trouble-filled item.
IF you can find/buy an "exact" match for your 2 older/OEM ignition coils (GM dealer, or junkyard
experimentation), that might be the cheapest place to start. If you can afford all-new ignition coils, ask a trusted local high-volume Auto Parts supplier to recommend the best part available for your specific vehicle. Just be aware that getting good/matched ignition coils may not be enough to fix some problems; you may also have a bad/intermittently-flaky/flaky-when-hot ICM; they are unfortunately all-too-common.
*Be sure to install the little devils with silicone di-electric grease around the contacts (and the 'mounting pads', if they exist on your specific setup), as recommended by your supplier.
And good luck...

[Teearohwhy]

wow, thanks for your detailed reply. You are correct. I believe the write-up for the procedure of testing the COILS, not the ICM, is in the 2000-05 forum. Strangely, after testing the coils and putting everything back together it was missing much more noticeably so I replaced the oddball coil with a brand new one. This coil read almost exactly the same resistence as the old one but eliminated the noticeable miss. I did finally check the DTCs. I started another thread related to this with more info I believe it is titled 'chugging up hills/flashing ses light' if you have time to check it out. Thanks for your suggestions!