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Multiple Ignition Control Module Failures

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Old Dec 16, 2025 | 12:58 PM
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It'* ironic that you mentioned that scanner because 3 days ago I ordered that exact Actron scanner kit off EBAY. It comes complete with all the cables and even a hard carrying case. I look forward to finally being able to read the codes. Thanks for your input.
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Old Dec 16, 2025 | 05:46 PM
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I'd like to know how you condemned the ICM? What tests proved it was bad.
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Old Dec 16, 2025 | 06:33 PM
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I will need to ask my mechanic that question. I know he did some testing on the first one that failed before ordering such an expensive part. I'll get ahold of him and post his response.
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Old Dec 16, 2025 | 06:42 PM
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I did find this information online and plan on running this test over the weekend when I have a bit of spare time. I will first try the unplug and replug sequence a few times as well as visually inspect all the wires for damage and/or looseness.

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Old Dec 16, 2025 | 07:11 PM
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I bought the car a couple years ago and it was love at first sight and drive. It'* like cruising around in




Lazy Boy chair. 😁 The power and smoothness of the 3800 are fantastic and the build quality of the car is remarkable. It'* sad that they don't make cars like this anymore.
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Old Dec 17, 2025 | 12:00 AM
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Nice one!

Very few of those left in the world, let alone in good shape!
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Old Dec 17, 2025 | 11:03 AM
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Thanks! She only had 68k miles on her when I found her 2 years ago. I've only added 6k miles since then. The previous owner had already flushed out the old Dexcool and replaced it with the regular green coolant. He also changed out the lower intake manifold for the improved Dorman model. The small plastic coolant elbow was swapped out for the metal one. All I've done so far was add new spark plugs and wires plus changed out the transmission fluid with Amsoil synthetic fluid and a WIX filter. I replaced the fuel filter too. I can't wait to resolve this ICM issue and get her back on the road... weather permitting.
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Old Dec 17, 2025 | 02:09 PM
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Very Nice car. When you ohm across the ICM outputs, please check the ohms in both directions when you post the results notating which lead was positive. I have a couple of ICMs, I'll compare your results. Also, please ohm the coil primary'* and secondaries (I have several of these as well that I can compare your readings). The clue that each time after replacing each of the ICMs, the car runs well for some period of time leads one to strongly suspect a loose connection or the one shorted wire on the ICM connector. If the insulation has worn though on the one wire, that should be visible with a bright light (but it never hurts to install a wrap or two of electrical tape where that wire could rub the connector both head). I've experienced the loose connection and it can be most illusive but if that is the case, I've had good success with tugging on each wire (one at a time) with the engine idling. Any change while your tugging on each wire is definitely a problem.

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Old Dec 17, 2025 | 02:28 PM
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Thank you for your input and advice. I hope to be able to begin all the inspecting and testing starting this Sunday. I will definitely post everything that I find.
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Old Dec 28, 2025 | 04:53 PM
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Happy holidays everyone! I apologize for not being able to do all of your suggested tests until today but here is what I did and found... I removed the coils and ICM and ran resistance checks. All 3 coils tested between 5-6 m ohms on the secondary side and .4-.5 on the primary side. I also purchased a brand new set of GM OEM coils and they tested basically the same. I then tested the output pins on the ICM. All the pairs tested at 5.3 with the tester leads in one direction and O/L in the opposite direction. I wire brush cleaned all 6 coil bolts as well as the module plug bolt. They looked good to start with but I did it anyway. The module plug wires showed no signs looseness or insulation damage. I re-installed the ICM with the 3 new GM coils. Operationally, not much has changed. The car doesn't start as easily as it should and it'* still down on power. It feels like it'* running on 5 cylinders. In neutral the idle is rather smooth but in gear you can feel the engine miss. Before I took things apart I hooked up an inline Lisle spark tester in-between each coil terminal and the corresponding spark plug wire. All 6 coils seemed to be producing a strong and equal power output. The car has 3 month old NGK plugs and wires. The fuel filter and air filter were also replaced at that time. I finally received my Actron CP 9145 scanner and tried it out today. It seemed to work fine and it gave me a trouble code for a lean condition and a failed camshaft position sensor. I just ordered an AC Delco sensor and I will install it when it arrives later this week. It seems odd that a camshaft sensor could be involved with this whole situation but who knows. It'* still very strange that 3 ICM swaps made the car run great for a few days before it started acting up again. I was really hoping that removing and re-installing the ICM plug would point to a plug wiring problem but no such luck. I'll post again after I change the camshaft position sensor. Thank you all again for your input. Hopefully, when I finally get all of this resolved, it will help out others.




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