fireaxxe

I went with the Mobil 0w-20 x2. The oil is physically green in color with the DexosD label on the bottle. After the change I noticed the cold start was dead quiet. Once warmed up the fuel knocking was at a much quieter but still there. I got my hands on a gallon of 5w30 Delvac Mobil 1 and topped off with 1 quart. The fuel knocking sound is gone. But went into regen and all the knocking and clatter returned but nowhere near as loud as it was before the oil change. I think the basic 0w-20 is just too thin for the diesel even if it is a light duty design. I plan on getting a UOA once I change it again.

Yes I have driven awhile and the truck is still smooth slowing down from 25mph. The main thing that solved this problem for me was removing the SQUARE lift blocks that came with the GM kit. I then replaced them with a TAPERED 2.25” lift block. I have removed the 3mm washers I installed between the transmission mount and transmission and noticed little to no change.

You were right. This morning it went from full down to half. I don’t know if this is a programming issue or the float was stuck. Anyone have this happen yet?

According to those calculations when I refilled it I had a total of 4.5 gallons then drove 1800 miles. I noticed that the manual list the total tank size at 5.3 gal. It makes sense that the last full bar represents 1.8 gallons of def when at full capacity. However I’ve towed for about 300miles and drove in various conditions for another 1500 miles and I’m thinking it should have used over gallon of DEF.

Had the crank no start, got the software update. Starting issue is gone now my DEF gauge is not working. Anyone else? C’mon GM get ya ****** together!

For those of us using the Amsoil dexosD oil. How do you like it? Has anyone done any UOA? Difference in performance or MPG? How does it sound? Any difference in engine clatter? Lastly, what’s the oil consumption rate if any?

I have heard that a few people have been just over a quart low on these. My oil level has never been low since new. They may have came from the factory a quart low due to the interruption in manufacturing and all the shortages that occurred during production.

I was interested in the Amsoil 0w-20 but it says do not use if Ck-4 is required. I am thinking the Cj-4/CK-4 bulletin might be a misprint in the supplement manual. I am also concerned about oil leaks that have been reported like the rear main seal. I’d hate to have a warranty issue because GM wants to blame non dexosD oil.

It’s listed in the 3.0 Duramax supplement manual. This is the online version for the 2020 model year. I found my hard copy and this is not the same information listed under the caution for the DPF. This must have been an oversight for the 2020 model year.

I have the same clatter, fuel knock, and pinging with mine as well. I notice it’s really sensitive to different fuels with BP causing the worst sounds from the engine. Love’s with 7 oz. of Stanadyne additive gives the best results for me. I’m also thinking the oil is way to thin for these diesels which is contributing to the noise.

I have been using this oil exclusively since new. I only have 4200 miles now, but I have noticed my engine has more clatter than it had when new. I thought it could be a few things like fuel quality but then I figured the oil was thinning out. So I changed it at about 3000 miles with no real difference in sound. Started looking around for another brand in hopes to find a better oil, and as we all know there are almost no dexosD approved oils on the the market. So I figured I’d go by the API and SAE requirements and noticed something interesting. The AC Delco 0w-20 dexosD has no rating on the bottle or anywhere that I can find. This top secret oil has very limited information available online as well. I then checked the 3.0 liter duramax owners manual supplement and noticed another strange detail. The manual says to only use CJ-4 or CK-4 rated engine oil or “damage to the DPF will occur”. I have yet to find a 0w-20 that carries this API rating and now I’m thinking that the AC Delco dexosD 0w-20 does not have this rating either. Does anyone know what the hell is going on with the required oil for this 3.0 LM2?

Just picked mine up from the dealership and was informed that they were able to recreate the crank no start issue and they “fixed” the problem. I was then told they updated the software and instantly my excitement faded away. They also did something to the regen cycle. It was in regen on the way home and I heard no knocking. In my state it takes 4 repair attempts and 20 days at dealership for the same issue to use lemon law, so one down 3 to go. Due to the fact that I am interested in a buyback I have to record every time I hit the start button for proof. Will post updates.

I have also seen the “Service steering column lock” message but it was when the wheel was turned and once I put pressure on the steering wheel to take the weight off the column lock I heard it click and the truck started just fine. Message has never come back.

I am FULLY aware there are no spark plugs in a Diesel engine. This is why I specifically said FUEL KNOCK. The timing of the Diesel engine is determined by the fuel delivery to the compression of the air that generates heat in the cylinder. In order to know when to deliver fuel the ecu looks at a number of sensors specifically the crankshaft position sensor and camshaft position sensor. So to reiterate my point, if there is an issue with the cam sensor this could cause not only a no start issue but also mistiming of the power stroke causing fuel knock and engine damage. I don’t think the 3.0 duramax has VVT The fuel was tested by a lab and was good and I only have a few thousand miles so no chance of significant carbon build up to cause a fuel knock. There is something wrong with these trucks.

There is something seriously wrong with these trucks. Yesterday while driving it went into regen and the engine was making the most god awful fuel knock I have ever heard. I am guessing if the cam sensor or reluctor/exciter wheel is the issue with the no start then the timing must be off while running at times as well. This would explain the fuel knock. I don’t believe the crank no start is the only issue related to this problem. There is no way this aluminum diesel will hold up to that. Yesterday I went to my purchasing dealer and requested a buy-back.

Yes I have what I consider rough shifts every blue moon. I also have the intermittent fuel knock that someone mentioned earlier. GM has had ground (-) issues before. I’m starting to feel like this is a nostalgic feature to remind us what cars were like in the ‘80s. But seriously every time I’ve had a stupid intermittent issue like this it was either a bad or loose ground connection or wiring connector. And after finding my battery cables with barely any torque along with the fuse box, I am certain there are other loose connections. I’d also like to share both times my truck ‘crunk’ and no start it was the first start of the day while sitting in my driveway. Hopes this helps you GM.

It definitely is fuel related. Compression heat is purely mechanical. I agree that it is also electrical but not a hard electrical fault. There may be some type of signal issue. I would think that if it was a fault there would be some kind of information stored and possibly a CEL. It’s acting as if there is a fuel kill function being activated or going into anti-theft mode. This is why I am suspecting the key fob since it runs everything.

Has anyone tried replacing the key fob battery? Maybe an intermittent weak signal or interference. I’ve replaced mine but not too confident this is the issue.

Just happened to my truck for the second time @ 1863 miles. Hit button crank no start then starts second try. I am glad I caught this happening on my ring camera good evidence for my buy back arbitration.

**Update** Test results came back and the fuel was good there is something else going on. Looking at requesting an injector QR code reset. Also developed a tapping at idle when hot. All the fuel knocking must have worn something out.

I’m glad you posted these details because I feel like my issues are a voltage issue. I noticed a few times that it seemed my battery was low it would crank just a little slower when I tried to start up. Also my voltage gauge would read low most of the time. I went ahead and purchase an AGM battery charger and put it on overnight. When I did this I went to remove the negative battery cable and noticed the 10mm bolt to the battery post was loose it was also loose on the positive side. So instead of removing the cable, I tightened them both down and charged the battery with them on. Hard to say if this will have an effect on the crank no start but I had a “creeking” sound when turning the steering wheel. That’s now gone away. And my rear driver side passenger door wouldn’t unlock first try intermittently. It’s worked fine every since. I think all these issues are related to a power issue due to loose connections and low voltage batteries. I also found loose hose clamps on the vacuum side of the turbo and one semi tight hose clamp on the pressure side.

That answers my last question

Same issue here 2021 RST Z71 3.0 Duramax 10 speed. Hit button, starter engaged ran for 15 seconds then stopped, truck didn’t start. Hit button again less than 10 seconds later then started. I checked the bolts on the fuse box in front of the battery and they were only about 25 in. Lbs. I set to 53 in. Lbs after finding this thread today. For anyone that has had the bent camshaft sensor exciter wheel was this accompanied with a Check Engine Light? And has anyone had the inspection only and DID NOT have a bent exciter cam sensor wheel? Lastly has anyone personally tightened the fuse box bolts and had a crank no start condition after tightening these bolts?

After researching a bit I found a few post and videos about the 3.0 liter Duramax and fuel knock. One person mentioned that he had the injector codes reflashed to the ECM and this solved his problem. I listened to the video and the sound was very similar to mine. https://www.duramaxdiesels.com/forum/threads/lm2-valve-clatter.84128/page-2 The video in post #39 sounded EXACTLY like my engine. Also see #35 the guy there explains the procedure and purpose behind resetting the fuel injector QR codes.

**Update** I went ahead and contacted the Department of Agriculture and Consumer Protection here in my state. I told them the situation and they informed me they were sending an inspector out to the gas station where I filled up to collect a sample for data analysis. I also learned that if you submit a sample of fuel from your vehicle they will test this as well. Once everything is back from the lab I will receive both test results. I am hoping to eliminate the possibility that I got a tank of “bad fuel” and find the real problem.