GM LML Diesel Pros Cons
 

Looking at a 2012 for a work truck,high kms but cheap comparatively.

Pros Cons ?

Supposedly Injection pump can be trouble if it hasn’t grenaded already. Only issue I had with my 2014 was def tank heater. Was a good truck otherwise.

Prone to headgaskets in those years, if they havent been done your on borrowed time along with the CP4 pump. Guy i work with just had this exact job done and with 2 new injectorsit was a 16k bill.

I traded in my 2016 LML at 50,000 km on a L5P to avoid the possibility of the fuel pump issue , although my GM diesel mechanic stated he had only done five pump replacements. The Bosch pump was made for European diesel which is much oilier than NA diesel. Problem is they can fail with zero notice and you are stuck wherever for at least a week while the nearest GM dealer replaces your entire fuel system (cab removal required) and then presents you with a bill for at least $12k. It’s apparently a way bigger problem in the US due to their fuel containing asphaltene molecules which destroy fuel lubricity. There’s some possible workarounds like adding lubricants to the fuel…

The other big issue with that generation of trucks is rust.

I’d buy one if someone swapped the CP4 for a CP3, or if the CP4 had already blown up and been replaced.

Overall, they’re great trucks but if your high pressure fuel pump goes, it’s going to cost you big dollars. And leave you stranded.

That said, I have had two 2006 Duramax trucks also require CP3 replacements so they’re not all infallible. Personally, I’d buy a Dodge… especially if stick shift.

Actually change my answer. Unless you really need the diesel for towing heavy I’d go gas truck. 6.2L Ford or 6.0L GM.

Saw some of those 6.2L Fords go to Ritchies from Suncor with 20-30,000 engine hours on ‘em. Probably 99% idle but still impressive stuff.

I understand everyone's reluctancy with the CP4 fuel pumps, as they were designed for European markets (Bosch) where they still have higher sulfur (lubricity) in their diesel fuel. The stats are around 7% of these pumps fail in North America, so nothing too crazy. However it can be a HUGE bill for the unsuspecting. In my 2011 Duramax I run a Lubricity additive, and at 280,000kms I have had no issues yet. Important to note that both Ford(2011-present) and Dodge (2019-20) use the CP4 pump as well, however they have lift pumps which seem to help the CP4 out quite a bit.
There are some aftermarket options that could help the OP if he gets the truck cheap enough, like an aftermarket lift pump or just convert back to CP3.

2011 LML duramax here.

If it still has the DEF in it, rip it out. It's surprising how much of a difference it made afterwards.

Hopefully you won't need to do head gaskets, they're pricey...

Rust above the rear wheel wells. Common problem. For the price I've been quoted it will be cheaper to buy a new(er) truck box.

Fuel filter is pricey. I switched over to the Sinister Diesel kit and now the CAT filters run me around 25 bucks a piece.

Thanks guys,turned it down.Had a lot of i$$ues.
Im now a little more knowledgeable about the LML and its problems.

Ive been a diesel mechanic for 45 years . My personal truck is a HD 3500 gas engine . Most of the guys in the shop go with gas also . Even our field service trucks are switching over to gas trucks .

That's interesting. I am wondering why?. Be great to hear as you have the experience and knowledge.

After towing with a diesel, it would be hard to go back to gas.

Field service trucks spend to much time idling, hard on emission components, company’s look at cost, gas engine is 10,000 less than diesel.


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LML duramax engines are known to snap cranks in stock form with no warning. That's $35k if you get an engine from GM. Not every one does that, but almost every time I look at Kijiji, there's one there with that problem.

LML also has the CP4 pump that likes to grenade. Years ago, Taber Diesel sent components out to be tested on a low miler that had that happen, and the guy swore he used extra lubricant in the fuel, as well as a few others. They claim that it was a heat treating problem on some of the parts.

The farm was looking for a truck recently. Called a friend of mine that all he does is Duramax repairs. He told me to get a LBZ or an LMM. If not deleted, delete right away. The farm got a LBZ 3500 dually crew cab. According to the gauge with a tune recently added, it's doing 13.7L/100km. I'll see what it actually is when I fill fuel next. Before the tune was put on, it was saying it was doing 15.5L/100km. Actual hand calculated economy was 15.8-15.9 L/100km pre tune.

After towing with that truck, I wouldn't want to tow with anything but more torque.

I was very specific when buying the 'new' truck for the farm that I didn't want to go newer than 2010. Too many problems, even though I would have liked the newer generation frame. But, I might see if I can get a newer frame and bumpers, and swap the rest of the truck over.

You can fix the fuel pump issue with a Fass fuel pump setup. I know a fellow that had a 16 grenade twice. Seven grand each time.


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LBZ LML? How do we know what year of trucks these are?
We have a 2012 with 65,000km on it.

You have an LML. LML is 11-16.
LBZ is essentially 06-07.5 to when then changed the body styles.
LMM is 07.5-10 essentially the new body style.
Then for fun, LB7 is the first duramax from 01-04.5.
LLY is 04.5-05.
L5P is 17 to present.

Then there are special purpose engines in the heavier trucks and cab and chassis packages.

There are vin breakdowns using the 8th digit of the vin that you can check on google.

These diesel trucks are more like tractors ,they are made for pulling hard every day and not just driving around town like driving to work every day .
A gas HD3500 can do that and pull a heavy load on weekends

Secondly the cost for using a diesel as your every day driver just does not make sense . If you add up the extra money it cost to get a diesel engine ,and the difference for an oil changes and fuel difference now that diesel is higher , plus the much higher repair costs on a diesel like $12,000. for injectors etc. Its just not worth buying one . I forgot you also need to add in the cost of a Jug of DEF once a month. Lol
If you add up all the difference over 5 years for owning a diesel truck I am guessing its about $50,000.more to own a diesel truck .
Now if you take that extra $50,000 ,and put it in a slush account you can buy a lot gas for your gas truck . So you are basically driving for free for the next 5 years where your diesel truck still has to fork out $50,000 more just on fuel alone

PS A lot of people say you can get more miles out of a diesel engine .
This is not true . Diesel owners pay a lot more to keep their engines
running to 500,000. km than a gas truck would . So if you would tell both drivers you can not do any major repairs outside of oil changes your gas truck would win and keep going . At work ,we have diesel and gas service trucks . The diesel trucks are always at the dealer getting repaired ,the worst part is ,they have no parts at the dealers ,so the driver is out of work for a few days where the guy that runs the gas truck is working every day . Lol Yup the diesel drivers wishes he has a gas truck .

PS again . Try finding diesel when going threw a small town .

Thanks Ive always wondered. Whats the price tag on a typical DEF delete job?

Depends on the shop. Some guys do better tuning than others. Best guy I know is Clay. Phone number 403-901-3694.

From what I've seen, he does some of the best tunes, and doesn't try to upsell nice to haves that are unnecessary.

Ask him about a CP3 conversion. Save your fuel system.