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Discussion Starter · #1 ·
So my 2021 GMC Sierra 1500 LM2 jusst thew a check engine light. Took it to dealer and was told "turbo overboost code". Cant even have it looked at for a month they are so busy which sucks because the wife and I had a trip planned to pul our trailer to Glacier National Park in about 3 weeks. Not happy.
Dealer also stated they had not ever seen this code before. Anyone ever have this?
 

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If you have other GM dealers in the area, you can use anyone that you like.

Does it reset on it's own?
Does the code return after being reset?
 

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Discussion Starter · #3 ·
The only other dealer is Reno, and they are the same - one month out.
Code showed up yesterday and did not reset on its own, and I just had the local dealer read the code this morning, and in the 20 min drive home the code did not reappear. Again the dealer said they had not seen this code before, and said it could be wiring, sensor, or a module. I am bummed that I may have to cancel my Glacier National Park trip which we have planned for the last year and a half. But I figure I will keep driving it for the next couple of weeks and see if the code pops back up before cancelling all my reservations. I also have a short trip camping planned close to home (~45 min drive) pulling the trailer, and I will be driving a mountain pass (~8000ft) so if the code comes back I suspect it will do so then.
This sucks...
 

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I definitely don't want to give you advice but I had similar situation with my F-350 throwing over boost codes. We were just about to leave on an extended trip pulling a 14,000 lb toy hauler when it did it the first time. I took it to the dealer who reset it and said they didn't find anything wrong. I bought a code reader and we left on the trip a week or so later. First day out we were headed up Cajon Pass pulling the trailer and the light came on again. I'd had numerous other issues and was so sick of the POS truck by then. I decided I wasn't going to deal with it during the trip as long as it would run. It ran fine throughout the trip so I just let it be. I reset that same code many times over the next 40 or 50,000 miles.

I hope you don't have to cancel Glacier. It's amazing.
 

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Get an edge insight cts3 so you can monitor your boost pressure and reset/monitor any codes..I wouldn't cancel my trip over it
 
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2021 Sierra Denali, S550, C6 Zo6, 1970 GTO LS1
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This is the first I have heard of that code. Havent read anywhere of it being an issue. The parameters to throw a code on this truck are pretty tight. So many resets and never another issue, tells me its pretty sensitive or tight parameters. We did Montana last year and it was awesome. We are considering Glacier late August or September to beat the crowds. I think the next week or two may tell you where your at. i would be calling every dealer around, dont cancel that trip...it may be nothing.
 

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The only other dealer is Reno, and they are the same - one month out.
Code showed up yesterday and did not reset on its own, and I just had the local dealer read the code this morning, and in the 20 min drive home the code did not reappear. Again the dealer said they had not seen this code before, and said it could be wiring, sensor, or a module. I am bummed that I may have to cancel my Glacier National Park trip which we have planned for the last year and a half. But I figure I will keep driving it for the next couple of weeks and see if the code pops back up before cancelling all my reservations. I also have a short trip camping planned close to home (~45 min drive) pulling the trailer, and I will be driving a mountain pass (~8000ft) so if the code comes back I suspect it will do so then.
This sucks...
Are you planning to take the trailer over Going to the Sun? (
 

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Discussion Starter · #8 ·
Any recommensdations on a CHEAP code reader/reset device. I looked at the Edge Insight that Wydopen731 above recommended and I just can't spend over $400 at this time. Also, where is the OBD port on this truck?
 

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I have reservations to stay inside the park for 5 nights, so I won't need a ticket to drive Going to the Sun Road. And, yes, the trailer will stay at the campsite for the GTTS drive!
Did you consider one of the parks tour 'buses' for the over and back?
 

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Pick up a Bluetooth OBD2 dongle from Amazon like the VeePeak for $30-$50 and buy a decent app like OBD Fusion for around $30. You can set it up to look at the PIDs and also read/clear codes with it.

Apples to oranges, but I had a Malibu for a while with 1.5 turbo. I got the turbo over boost code on that car once around 40k miles. I took it to the dealer, they didn’t find an issue, reset the code, and I drove the car another 80k miles and it never reappeared.

I would drive the truck as much as you can between now and your trip. It’s possible there’s not an issue, just the ECU seeing some out of spec numbers for a second due to a fluke. If there’s a real issue, the code will come back.
 

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Discussion Starter · #16 ·
Yesterday I went and talked to the service writer who I originally spoke to at my local dealer and he assured me that the code would still be in the computer, so this morning my wife and I took separate cars and drove 2 hours for a dealer appointment in Placerville, CA. Since we had driven so far the service writer said he would get the truck to a tech right away on the very slim possibility that I would not have to leave it. Well guess what? There was no code in the computer. The bastards at my local dealer erased it and then lied to my face. The writer at Placerville said to go have lunch, and after an hour or so called me. He had called GM and there was no known issue with this code and the LM2. Furthermore, if that code pops up the truck is supposted to go into limp mode, which obviously mine did not. He also had the tech check the turbo bolts, actuator bolts, checked the turbo for leaks, etc. All was good. Drove 2 hours back home and truck ran flawless. So as of now, all is well, and Glacier trip is back on. Bottom line, Michael Hohl GMC in Carson City, NV sucks, (won't be going back there....ever) and kudos to Thompson GMC in Placerville CA. They know what customer service is all about! Wish Thompsons was closer, but any warranty work going forward will go to Reno, which is only 40 minutes away...
 

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Good for you, enjoy your trip. Have read of several little issues and a couple of bigger ones (rear seal) but never this code or over boost. I had the long crank, which was a software update. I also had the coolant pump and kinked hose first week i had the truck. Several others had same issue, and they actually just redirect the hose. 12k and the truck has been a joy, love it. We buy GMC's so we can service them anywhere in the US, so just enjoy your trip, and dont sweat it. Trying to clear up our life here because we are seriously considering Glacier ourselves end of August. We shall see. We did Montana last year but it was May and GTTS road wasnt an option so we didnt go all the way north. Snow in May???? Who knew!!! LOL
Good luck
 

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Discussion Starter · #18 ·
Good for you, enjoy your trip. Have read of several little issues and a couple of bigger ones (rear seal) but never this code or over boost. I had the long crank, which was a software update. I also had the coolant pump and kinked hose first week i had the truck. Several others had same issue, and they actually just redirect the hose. 12k and the truck has been a joy, love it. We buy GMC's so we can service them anywhere in the US, so just enjoy your trip, and dont sweat it. Trying to clear up our life here because we are seriously considering Glacier ourselves end of August. We shall see. We did Montana last year but it was May and GTTS road wasnt an option so we didnt go all the way north. Snow in May???? Who knew!!! LOL
Good luck
Yeah...From what I read GTTS sometimes doesn't even open until July - you never know so it's a crap shoot going in spring or even early summer. We scheduled our trip this year to be there until the park closes for the season on Sept 5 I believe.
Zero issues with my truck except for two extended cranks in 12k miles. Then this glitch with the P0234. If you go back to Glacier maybe we will run into each other. Have a good one and happy camping!
 
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