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Discussion Starter #1 (Edited by Moderator)
Ok, so I have a check engine light come on and since it was still under warranty I took it into the GMC dealer. Turns out it was, according to them, #8 glow plug was bad. Not a warrantied item and wanted $500 to fix. I said, na , Ill get it. So bought one and just replaced it. Well I disconnected the battery for about 20 min while doing it and figured with any luck the check engine light might reset it self. :facepalm: longshot but hey, if not advanced or autozone will do it. Turns out they dont do that anymore so I asked them to just read the codes to me and it came up with P0678 P16a8 and p0675. According to gm it was just #8 and not #5 or the glow plug control mod. Does anyone know if the control mod code generally shows up in conjunction with the glow plug code? Thanks

2015 denali 2500 with 70k
 

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One will become 2 will become 8. Trust me on this. Do all 8 with AC Delco plugs. I did the one, then another coded so I did the entire bank and then one on the opposite side went. It's a current or resistance comparison type thing.

I sure would have thought this would be warranty though.
 

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Discussion Starter #3 (Edited)
One will become 2 will become 8. Trust me on this. Do all 8 with AC Delco plugs. I did the one, then another coded so I did the entire bank and then one on the opposite side went. It's a current or resistance comparison type thing.

I sure would have thought this would be warranty though.
Nope, they considered it as a sparkplug equivalent. Anyway to reset the check engine light myself without reader?
 

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I bought my LML new.

Had one glow plug replaced under warranty (2nd or 3rd winter iirc). Never had to replace another.
 

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Nope, they considered it as a sparkplug equivalent. Anyway to reset the check engine light myself without reader?

Search on Amazon, I have the basic model and it read's & resets/clears codes.

"Autel MS309 Classic Enhanced Universal OBD II"
 

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All my glow plugs have been replaced under warrenty as they went bad. One would go bad. I would bring it in and have it replaced then in a few weeks another one would go bad. I would bring it back and have it replaced. I did this until all were replaced. It was APITA to keep going back..
Don't believe the dealer when they tell you something isn't under warranty.
Because of a known issue with the glow plugs on the 2012's GM extended the warranty on them to 10 years/ 120,000 miles...
The dealer tried to tell me mine weren't covered. Then I made them look it up and they saw that they were.
This has happened to me on several occasions where I had to argue with the dealer.

GM has extended the warranty to 10 years/ 120,000 on the 2012's for:

Glow Plugs- Mine were replaced
Indirect fuel injector ( 9th injector in the exhaust)- Mine was replaced
DEF tank and components- My tank was replaced.
Engine exhaust pipe for diesel smell during region.
 

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OP's should be covered on the original factory warranty, since the truck is under 100k and under 5 yrs.
 
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