Hello,

I have a 2021 Chevrolet Tahoe 3.0 Duramax with approx. 20,XXX miles. I am currently dealing with the check engine light coming on every 80-90 miles of driving and clears on its own after driving another 30-40 miles. I dropped the car off 2 different dealership and pretty much did not get any much help due to the fact the engine runs normally even with the check engine light coming on. However, I do notice that the RPM gauge does fluctuate about 400-800 (barely noticeable). The last time I drop the vehicle off to our local dealership, the technician (on the work order invoice) stated that he could SMELL gasoline mixed with diesel and that it could be the issue.... I think its more of his own BS that he smelt. I have another appointment at another dealer that has high rating for their diesel service. I have reached out to GM corporate and was advise to request for a GM certified technician to assist with the troubleshooting if the dealer technician fail to find any resolution to the diagnosis.

Any help from any GM technician certified with repairing diesel engine would be greatly appreciated.

What I don't understand is why haven't any of the 2 dealer ship I've taken the vehicle to have taken the initiative to look at all parts that would associate with the code?

Can you get us a list of codes that are stored while the light is on?

This is a pretty big fluctuation.

Does this happen while idling or driving?

. . . from what RPM to 400RPM higher? Like 600-1,000-1,400 or 800-1,200-1,600 or . . . ?

This is an accusation of misuse and damage. I wouldn't let that go unanswered, especially since it is now documented. They can certainly test the fuel to know for sure.

Did they put the stored codes that they found on the invoice?

I'm not taking sides here, but doing this could be a wild goose chase for them. At the same time, I can't tell from here that they didn't look at everything. That being said, even if they did, the issue might not be easy to find. It is so marginal that it fixes itself twice as fast as it has the problem.

I have this up coming appointment to drop the car off at a 3rd dealership, if for some reason this dealer isn't able to figure the root cause of the code. Am i able to request for a certified GM technician to come out and assist the dealership with the diagnosis? I was told by the GM corporate service dept. wasn't too sure of the process but does sounds like an option to go with if all else fails.

Dealers use ASE and factory certified technicians. They may call corporate for help in warranty issues which I would think this qualifies as.

Just wondering if anyone else came across this code with any newer duramax 3.0 engines.

This may help.
https://www.duramaxforum.com/threads...-p1089.980415/

I don't recall seeing this here for at least the last few years.

I like this thread. Learning stuff!

Moved thread from the "Chevrolet" forum to the "GMC/Chevrolet Truck/SUV" forum.