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Hey guys, new to the group. Looks like a TON of great information on here. I’m about to purchase my dream truck (2019 Duramax Denali) after a pretty rough accident totalling my previous 5.3 Sierra SLT.

I’m a carpenter, far from a car guy let alone a Diesel guy! Is this a good year? Anything I should be particularly worried about?

2019 6.6 L5P 2500 Denali, certified pre owned, 56k miles. I appreciate any insight! Thank you!
 

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Do not buy it the 2017 L5p straight up garbage it's the problem child of the L5p
My truck is currently in the shop getting fixed once again the DPF system cloggs up with no tune it doesn't Regen like it supposed to ecm will loose communication then check eng ligh the I lost an injector driver and I shut it down and got it towed and now the shop is telling me I need a new motor because raw fuel mixed with the oil and dryed up the bearing an know I have a dead cylinder with only 133k on the truck and have only owning it for 4 months yeah I guess I need to research before spending 55k on a lawn ordament

yeah this list can roll on for ever.
not like the truck stuck broken down
 

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2021 Silverado 2500HD LTZ L5P
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Tow heavy loads?? Drive longer distances??

If not prolly not a good idea. Modern emissions diesel need to be driven a good bit regularly.

I do tow a heavier trailer occasionally and would have been fine with a 6.6 gas motor but for me it was more a want than a need. I do drive longer distances a lot so I can get the truck hot and run it for a bit. I would have loved the 3.0 lm2 if it had a bit better tow rating.

I love my l5p it's a 2021 but I'm not a fan of used vehicles. Reason why is usually the previous owner got rid of it for either it's a problem child or warranty expired and they are having pricey issues or cant afford payments. Or a mixture of all that. We also just had a major hurricane in florida so peeps are selling flooded vehicles around the country. DO YOUR RESEARCH. if you are buying used.

Every used vehicle I've purchased has had major issues I had to fix but I bought them knowing it was likely to be the case. I've had 4 used vehicles in the past and still own 1.

One of the biggest issues with earlier l5p is glow plugs breaking. Dealerships will get a older l5p in with a glow plug error and just keep resetting the codes until one cracks and ruins an engine. If I was buying an older l5p, older than 2021 i would just replace all the glow plugs out of hand just to be sure. The other issue with older l5p is they can sometimes burn out the injector connectors but that is not going to ruin an engine the way a broken glow plug will.

There is also def heater/tank issue that may rear its head on older l5p if you buy a truck that is from a warm climate and have a good solid cold snap. It may have never been updated with current tsb programming for the heater.

One last thing... everything a salesman says to you is a lie. Period. When you buy a used vehicle you are making the proverbial deal with the devil and the devil is never left holding the short end...
 

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2017 Chevy Silverado 3500HD LTZ Z71 L5P CCSB
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I've got a 2017 with 125k miles on it now. It's been a reliable truck, but there are some problems you're definitely likely to encounter.

They seem to go through glow plugs much more often than other trucks; my 2017 has had around 10 glow plugs replaced over its lifetime. There was a software update released that may or may not have fixed this problem, and I haven't had to replace any in the 15k miles since I had mine updated.

Injector connectors have a high failure rate. You can buy replacement crimp-on connectors for around $50 each if you want to try a DIY replacement. I haven't had to replace any on mine yet, but it's just a matter of time.

The coolant reservoir has a built-in sensor that fails. When it does, the entire tank has to be replaced, and replacement tanks are around $100. Not a difficult job to do with some basic hand tools.

Modern emissions diesels also do better when driven at highway speeds for extended periods of time regularly. The DPF can clog up quickly otherwise, since it won't get warm enough to start a regen and clear out the collected soot. You will notice when a truck starts a regen in town, since it'll idle much higher and the burning diesel smell is much stronger, at which point you'll want to take it for an extended drive as soon as possible.

Other than that, they're good reliable trucks and they'll treat you right as long as you treat them right. Keep up on your maintenance, use quality diesel and DEF fluid, and you'll probably be fine.
 

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Well I must be lucky to not have a single problem from my 2019 L5P. One upgrade I do highly suggest is a Banks in line tuner. Allows you to monitor soot levels and manual regen as needed. Keep those soot levels low! You wont regret the purchase. Congrats!
 
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