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Discussion Starter #1
My car is a 2003 Impala LS with a 3800. After driving for about 20 mins on the highway I noticed a little loss of power. By the end of the off ramp it was missing badly and running like crap. My cel came on and started to flash. After checking the code with a pocket scanner I found it to be code P0300. I reset codes and it came back right away. I found cylinder #2 and #5 had no spark at the plug, then check at coil no spark. I replaced plugs, wires and all three coils. Still misfiring on same two cylinders which are on same coil. I have 12 volts at terminal two on module of all coils but do not have an led test light to check for switching on terminal 1. If the car sits overnight it runs perfect for about a min or two then light comes back and so does the misfiring.

Here is what I have check and or replaced so far:

1. new spark plugs
2. new wires
3. looked for vacume leaks with carb cleaner
4. repalced coils

No spark at coil leads me to an ICM, my question is am I on the right track or not?
 

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Discussion Starter #3
About sitting overnight, or about replacing coils?
 

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8th Gen Antagonist
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13,660 Posts
I'm still thinking ICM, they are very temperature sensitive, so I'm not surprised by that.
 

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Discussion Starter #5
I am going to radioshack today and picking up an LED light to make a test lead to see if the ICM is switching on terminal 1 as I have 12 volts on terminal #2. If the light blinks the while cranking the ICM is good, If it does not then it is bad.
 
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Discussion Starter #6
ICM failure, replaced and all is well now.
 

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Back in Black
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glad you got it fixed :eek:k3: motor on
 

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8th Gen Antagonist
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Breaking out the smarts on this one eh? Good idea with the led tester!
 

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Mr. Handy
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ICM failure, replaced and all is well now.
Did you apply thermal paste in between the ICM and bracket (actually a heatsink)? If not, it will likely overheat over time and fail once again.
 

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Discussion Starter #10
Actully I forgot to buy some but I had some left over termal paste from my new CPU install on my PC so I used it. Found the LED idea from diagnose my car dot com, wish I could take the credit on that one.
 
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