Seized engine or not?
 

My GL350 Blutec died on me about 100 yards after I drove off from my house. Just stopped. To me it looked like the battery suddenly died and I could see how it was draining in front of my eyes. So the car got towed to a near by shop where they put both new batteries in, the small one and main battery. That didn't help. Mechanic told me that engine is seized and won't turn. So I took his word for it and we towed the car back to my house.
Today, a mechanic friend of mine stopped by and ran some diagnostics and found bunch of codes saying "No CAN messages received from engine control unit and "undocumented codes". He also noticed that started is not kicking in when turning key. So he is saying it could be electrical issue since nothing engaging when key is turned on. Car makes no sound at all. Just turns all warning lights and "add bluetec" sign.
What do you think? Seized engine or not?

Does the engine turn manually? It's more likely the CAN died if you have no communication.

Same happen to me, car just died after 50 miles trip without any noticed just stop. I thought it was an electrical problem until I tried to move the engine manually, was solid I had to use a big breaking bar and 4 feet tube to move 1 inch.The oil level was fine, the viscosity looks normal and the car did not give me any indication of a problem, I purchased few months ago with 55k miles less of 20k miles later is just a sad reminder of never buy a luxury car without warranty.
My friend say the lack of oil was the cause of this problem. no way to fix that block.
Up to now the engine block cost around 7k to 10k plus labor (may be 5k ?) , crazy expensive, so probably will check at copart website to see if I can find a crash car with a good engine , way cheaper that try to get a rebuilding block.

So oil pickup some how got blocked? What exactly caused it?

May be is the lack of oil flow inside the engine, some guy from Houston tell me (he rebuild and sold some engine block) told me he oversize the oil pump plus he add some new oil sensor ports if you want it.
I still have not opened the engine to check what internal damage it has and probably will not. a mechanic told me that practically those block can not be repaired and that surely everything has been welded inside by the friction and heat, the only reason that happens is due to lack of oil.
there is another person here with the turbo and has a video where no oil reaches the turbo, may be that happen on the entire motor
just guessing.

Nope, couldn't turn it with standard crankshaft . So i thought seized engine for sure.
The weird part is that batteries died when it came to stop. Just like something drained all power. Put both new batteries in and now when I turn the key it doesn't even click.

I will be going to dealership where I bought it and asking them for some sort of fair trade-in value if I buy new car. Otherwise I'm stuck with that junk in my garage.

I would love to see your oil sample sent for analysis.
A side note, I wonder if oil pickup from the pan is compromised with time due to pressure drop caused by faulty seal? A closer look at the oil pickup is worth investigating...

Every seized v6 diesel we had was a bearing in the middle of the engine failing. Curious to open it up and see what it was. The last one I did put a rod through the block on one of the middle cylinders.

On my next oil change, I'm thinking of removing the oil pan and changing the O ring gasket at the pickup tube. Looks like MB updated that Oring from black to green composite material. They did not update the oil pump on crankcase square gasket (A 642 181 00 80).
Attached is what I'm thinking of changing.
https://cimg2.ibsrv.net/gimg/www.mbw...da2dfecac1.jpg