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2009 CTS AWD
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Hey guys/ladies! Of course, my husband is out of state and my car breaks down. I have a little more than basic knowledge of mechanicin'. I have a 2009 CTS AWD. 111,000 miles. Bought it used in 2011, no warranty left. Check engine light is on. Car became weak and started misfiring. I started with the most obvious (cheapest) and replace the plugs, no change. A week later, I smell plastic burning, blatant loss off power and it was obvious a cylinder was dropped. (Flashing check engine light) Limped it back home to find out coil pack #3 was melted. Got a new coil pack and installed it this morning. Car ran amazingly for about 10 minutes... Melted again. Gotta be a short, right??? Pigtail maybe? Suggestions?
 

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'05 CTS-V
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8,040 Posts
It does seem like it's gotta be something wrong electrically. I assume the plug that came out of #3 looked fine when you replaced the plugs? Have you pulled the new plug, just to be sure it's good?

I would think the coil packs are all grounded together, so it seems strange that only one would be dying. I guess trace the wiring harness and see if you find any faults.
 

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2008 CTS 3.6 RWD LY7, FE2
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55 Posts
It does seem like it's gotta be something wrong electrically. I assume the plug that came out of #3 looked fine when you replaced the plugs? Have you pulled the new plug, just to be sure it's good?

I would think the coil packs are all grounded together, so it seems strange that only one would be dying. I guess trace the wiring harness and see if you find any faults.
If im not mistaken, the coils ground themselves to the head. I have not had the chance to look at these particular coils but there could be an issue with the new coil not properly shedding heat into the head. Perhaps not torqued properly or something that would cause excessive heat buildup?

coils operate by receiving voltage to charge and the ground circuit is closed by a signal from the pcm causing spark. All grounding should be done at the coil to head interface. perhaps low voltage is causing a problem, low voltage typically means higher current and thus joule heating aka toaster. do you have a voltmeter handy? may have to have someone with a tech2 watch coil voltage while running.

thats all the ideas i have at the moment, good luck.
 

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2012 CTS
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11 Posts
What was the condition of the original spark plug that was on the failed cylinder? Did the plug on the cylinder that just failed look ok? Another possibility is a failing fuel injector causing the cylinder to get hot, but that is probably a long shot. You need to use a meter to ohm out the harness to make sure there is not melting further down caused by the melted coil...if the wire connector has heated up enough to cause the coil to melt it is probably bad now.
 

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03 cts 3.2L, 08 cts4 3.6L DI
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I had this problem on my 08 cts awd 3.6 di. Coil 3 melting causing misfire, CEL, ect. gm said ecm bad, replaced, put new coils in, happened again a month later. 2nd round repair, 3 months in shop, finally concluded it was fuel injectors shorting out. Replaced all, and back on the road. Ran great for a year, then last week, boom, misfire, NO CEL, and I have a melting coil #3. Taking it in again this week, hope it's something easy to find because Im losing trust in this car. My 03 cts still runs like a dream.... Let me know if your repair turns up anything
 

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03 cts 3.2L, 08 cts4 3.6L DI
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Cadillac Customer Service reps have any info??? This has been a major issue since I've had the car..
 
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Cadillac Customer Service reps have any info??? This has been a major issue since I've had the car..
Hello njskillz,

We are sorry to hear about your concerns regarding the coils in your CTS, and we realize how frustrating it can be to require multiple repairs for your vehicle. Unfortunately, we are not certified technicians and would not be in the best position to properly diagnose this concern. However, if you wish to proceed by working with a Certified GM dealership I would be more than happy to assist with that process.

Sincerely,

Samantha N
Cadillac Customer Care
 

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03 cts 3.2L, 08 cts4 3.6L DI
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Thanks Samantha,
The car is currently at my local Cadillac dealer. Was just hoping your team may have some insight on the problem, or be able to find out if there were any repairs done for this issue on anyone else's CTS(or other GM vehicle with same engine) that solved the problem.
 
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Thanks Samantha,
The car is currently at my local Cadillac dealer. Was just hoping your team may have some insight on the problem, or be able to find out if there were any repairs done for this issue on anyone else's CTS(or other GM vehicle with same engine) that solved the problem.
Hello njskillz,

You are very welcome. Please keep us updated on the status of your visit to the dealership. As always, feel free to private message us if we can provide additional assistance.

Kind Regards,

Samantha N
Cadillac Customer Care
 

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Traded in that boat anchor
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129 Posts
Please let us know what they find as I have a slight miss, noticable more at idle and was leaning towards a coil issue also.
 

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Did you see any oil in the spark plug tubes when changing out the plugs? GM had some supplier issues with the cylinders heads on 2010-2014 CTS's because of porosity. This maybe linked to your coil pack shorting out if there is enough oil in there. However, my bet is on the PCM. I had the same problem on another car of mine and a replacement PCM fixed it.
 

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03 cts 3.2L, 08 cts4 3.6L DI
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Mine is a 2008(3.6 DI AWD), so not sure if it has the same oil issue you spoke of. When the problem first came up I changed plug and coil #3(the melting one)and don't recall noticing excess oil. New coil melted 100 miles later. Took it to dealer, they tried messing with the grounds, didn't find anything. Eventually replaced pcm and all coils and reprogrammed. Lasted a few months, then coil #3 melted again. 2nd visit took a few months before they concluded shorting fuel injectors. Replaced all the injectors and it ran well for a year. Coil #3 again now. Been in the shop for about 3 weeks, haven't heard any news yet. I'll def keep this thread updated because I can't imagine that me and the other user Enid are the only ones with this problem.
 

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How can you go without a car for 3 weeks if it's a daily driver. Sounds like it's sitting in the back of the shop collecting dust. I hope you are able to figure out what's causing it.
 

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03 cts 3.2L, 08 cts4 3.6L DI
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How can you go without a car for 3 weeks if it's a daily driver. Sounds like it's sitting in the back of the shop collecting dust. I hope you are able to figure out what's causing it.
I also have a 2003 cts, so at least I still have some reliable wheels :wink:
 

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03 cts 3.2L, 08 cts4 3.6L DI
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They have to have the problem happen again while they have it, so I'm sure that's why it takes em so long. They can only run it and drive it for so long during a normal work day. When it first happened, I replaced the coil pack and reset the code, and it took about 100 miles of driving before it happened again.
 

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03 cts 3.2L, 08 cts4 3.6L DI
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Most recent update: Got car back in late November. Cadillac dealer had it for about 6 months, couldn't find root of this occurring problem. They spoke with a GM engineer whose only insight was possible causes they have checked/replaced on prior visits(ecm, grounds, wires, fuel injectors, ect.). They replaced entire harness for the #3 coil, replaced coil pack(all under repair warranty from same issue last December), and idled/test drove for about a week. No issues so far, but since no cause was ever really found for sure, I can't trust this car. Probably will end up getting rid of it. It's a shame cuz it's such a beautiful vehicle, but it's literally been at the dealer service shop for about half of the 3.5 years I've had it...No love lost for Cadillacs yet, just bit into a bad apple I suppose.
 

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SOLD - 2010 CTS4 Premium Wagon-Diamond White-Cashmere Interior
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Don't believe everything you read on the internet! :)
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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