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Discussion Starter · #1 ·
Somebody has got to have a answer to this. My brother has a 06 cts with a 3.6l engine about 9 months ago he had a code that his purge valve was malfunctioning, so I replaced it for him, it lasted about one week and it happened again, so I replaced the part and installed it. Now at the same time it flashed a code for oxygen sensor, I fixed that but immediately that code disappeared and a new one popped up for faulty catalytic converter. At the same time every once in a while the engine would stumble, it seemed like a misfire, but no codes, this was random like once every couple of days, also at the same time one of the headlights would turn off and on and was a different headlight every single time. Now I fixed all the problems but the engine stumble and the headlights, but now it stumbles 100 times a hour and headlights turn off and on like a disco and like i said theres no pattern it's as random as random can be. The car has 140,000 on it and runs like a scalded dog but you can't drive it after dark and hasn't been for 3 months now. I'm no master mechanic but I've been working on everyone's vehicle for 40 years. I've layed awake at night just thinking of anything that I might have missed and my brother loved that car and was so proud of it, but now he's talking about selling it or just taking it to the crusher. He's racked his brain as well and me and him have done more research than the cars developer's have. I cant understand how this doesnt throw one single code and I've read online that this has happened to countless others but GM still doesn't no what this is and will not look into it. I find this unacceptable, someone, anyone please tell me what to do next if I have to look at this man's disheartened face one more time. Can anyone help ? Scott
 

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2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
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Weird thing like this are frequently a ground issue. That is a point where where seemly unrelated systems can share a common failure point. Look at the core support or other front end sheetmetal parts that have ground fasteners on them. Look for loose connections, corrosion on ring terminals or broken wires. I will check tomorrow and see if the schematics show any ground point that would.be common to both headlamps and either ignition coils or fuel injector. I will let you know what I find.
 

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I did some quick research and came up with this..
G104 ground point is common to all the headlights and the ignition main relay. This relay provides one source of ignition 1 voltage to the ECM
G104 is located "On the right front corner of vehicle, on the right body rail near the right headlamp."
A loose connection there would cause the headlamp flicker and might be the cause of the engine stumble.

Hope that helps.
 

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06 CTS Sport/Luxury package
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If the above ground terminal does not fix the engine stumble. Then it might have a misfire. Unfortunately for you, ”small” misfires for this car does not throw codes.

For each of my misfires, I had to go to a shop to hook up a scanner that can do live codes. The screen I went to would have a list of all 6 cylinders with a 0 next to them. Whenever a misfire occurred, that 0 will start to count upwards. Most of the time it was in a single cylinder. first time was cylinder 2 and the second time a year later it was cylinder 3. Both times it was the coil pack that failed. Neither threw a check engine light.

KOT
 

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Discussion Starter · #5 ·
Weird thing like this are frequently a ground issue. That is a point where where seemly unrelated systems can share a common failure point. Look at the core support or other front end sheetmetal parts that have ground fasteners on them. Look for loose connections, corrosion on ring terminals or broken wires. I will check tomorrow and see if the schematics show any ground point that would.be common to both headlamps and either ignition coils or fuel injector. I will let you know what I find.
Much appreciated, im leaning towards the same thing I've already had the bumper cover off just this last week but what I'm afraid of now is that a short or something of that nature has corrupted the ecm or bcm r maybe both.
I did some quick research and came up with this..
G104 ground point is common to all the headlights and the ignition main relay. This relay provides one source of ignition 1 voltage to the ECM
G104 is located "On the right front corner of vehicle, on the right body rail near the right headlamp."
A loose connection there would cause the headlamp flicker and might be the cause of the engine stumble.

Hope that helps.
Hey thanks for getting back to me so fast I'll look into it tomorrow when i go by his house, and I'll let everyone know on here. thanks again
If the above ground terminal does not fix the engine stumble. Then it might have a misfire. Unfortunately for you, ”small” misfires for this car does not throw codes.

For each of my misfires, I had to go to a shop to hook up a scanner that can do live codes. The screen I went to would have a list of all 6 cylinders with a 0 next to them. Whenever a misfire occurred, that 0 will start to count upwards. Most of the time it was in a single cylinder. first time was cylinder 2 and the second time a year later it was cylinder 3. Both times it was the coil pack that failed. Neither threw a check engine light.

KOT
After moving some wires I did find g104 and g110 both were extremely rusted , think about this, after spending a shitload of money on a luxury vehicle you start having problems like i describe, only to find out the only reason your having these problems
Auto part Fuel line Vehicle Engine Car
is that they used regular bolts instead of using something rust resistant, unbelievable. But back to the fix , on g104 I found what my mechanic friend calls GREEN DEATH ! What i did was sand and grind the shit out of it and bolt it back up. Tomorrow I'll stop by and bring some spray paint so this wont happen again. And yes it fixed the headlight problem but not the stumbly wumbly engine but there's hope i only have to track down 17 more grounds........ugh!! I'll let you know what i find out. Thanks for the help !
 

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Much appreciated, im leaning towards the same thing I've already had the bumper cover off just this last week but what I'm afraid of now is that a short or something of that nature has corrupted the ecm or bcm r maybe both.

Hey thanks for getting back to me so fast I'll look into it tomorrow when i go by his house, and I'll let everyone know on here. thanks again

After moving some wires I did find g104 and g110 both were extremely rusted , think about this, after spending a shitload of money on a luxury vehicle you start having problems like i describe, only to find out the only reason your having these problems View attachment 578641 is that they used regular bolts instead of using something rust resistant, unbelievable. But back to the fix , on g104 I found what my mechanic friend calls GREEN DEATH ! What i did was sand and grind the shit out of it and bolt it back up. Tomorrow I'll stop by and bring some spray paint so this wont happen again. And yes it fixed the headlight problem but not the stumbly wumbly engine but there's hope i only have to track down 17 more grounds........ugh!! I'll let you know what i find out. Thanks for the help !
Glad I helped a little bit at least now it is safe to drive at night. If the ring terminal was green I am worried that the ground wire for the Ign 1 relay may be compromised. The moisture and corrosion you saw can work it's way into the wire insulation and destroy the wire several feet away from the ring terminal itself. The Ign 1 relay ground wire is the pink 18 gage one. The best way to check it would be to use an ohm meter and check the resistance from that ring terminal to the Ign 1 Relay in the under hood fuse block. I cant tell which of the 4 terminals it is but one of them should be less than 5 ohms to that ring terminal.
I would add one thing. You mentioned the ECM or BCM being corrupted by the fault.
I have worked for GM since before cars had computers. I have supported recalls and campaigns at dealers. I have worked on one off cars. I currently do at work just what I did for you. Sometimes for vehicles that dealers can't fix sometimes for 2023 or 2024 model year vehicles. In all my work I have replaced exactly 2 bad computers. I know dealers replace them all the time but a huge percentage of them are just fine. It is the act of unplugging the old and plugging in the new computer that normally fixes the bad connection on one of the 100 or so terminals. A few weeks later the problem returns and then, because the computer was just replaced and it won't be covered under warranty, the bad connection is found and fixed. The "bad computer" isn't really a thing. They can fail, but the failure rate is extremely low.
 

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Discussion Starter · #7 ·
Your probably right , I think the I brought it up was I work out pf a 92 dodge dakota and i broke down 20 miles from the house. My friend had AAA and didnt cost a thing, very cool of her! But everybody said anything from the fuelpump and its a relay and even GREEN DEATH !!! But after checking everything out before I bought one thing ! I found there was only one thing it could possibly be by deduction alone, The Computer .... thats a hint people do your tests and you don't have to empty your wallets and will defiantly leave something out there for are children to inherit. Stop spending frivolously . Sorry about that....thats the reason for the mention about the computer, fixed it and I had to check everything out first anyway before i lost the warranty, you fry it you buy it....lol
 

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Discussion Starter · #8 ·
Number 4 coil pack was bad that was the reason for the engine stumble, checked the resistance and it was 4 times higher than other 5 cilynders, car is finally fixed . Thanks again for your assistance
 
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