Engine Seized or Any Other Possibility?

[Davsha]

Greeting to All,

2012 E350 W212 OM642 111K miles.

For 2 months, been chasing a too slow cranking, cuts off after 5 secs, no start. condition.
Had many DTCs come & go. "Solved" most of them, with no change in the symptoms.

One week ago, things worsened to a no crank at all, no sound whatsoever. Dashlights work.

Removed the starter & it works. Tested directly from battery & also with an auto electric specialist.
Can NOT bar the engine over at crank pulley, with any ammount of force. Tried with belt loosened also.

Need to mention that my latest persistent DTCs include:
P008700 low fuel pressure (prob not relevant with no crank).
ISM NOT taught in. But when I tried to "teach in" with code reader says "already taught in".
I did have the "Do Not Shift, Visit Workshop" for a few days. Cleaning the ISM plug SEEMS to
have solved that. Time will tell.
Also have come & go "no comms" codes.
SO, does anyone know if a confused ISM is capable of mimicking a "seized" engine condition?

Before I possibly give up on this bit__, wanted to see if there could be another possibility than the obvious one.

Thanks in Advance,
Sara

 

[Ted]

How is the battery/engine/chassis earth connection?
What is the battery voltage during cranking?

 

[Davsha]

Battery is a new OEM spec Weitz. Grounds checked.
Battery voltage before cranking is 12.8. Starter is now out, so not relevant.
As I mentioned, can NOT turn engine over by hand using a 27mm on a 1/2 breaker with or without a pipe.

 

[Jobsworth]

The ISM won’t be locking the engine. The only possibility that is outside of the seized engine scenario is if the torque converter has become welded to the bushing in the transmission oil pump.

 

[Davsha]

The ISM won’t be locking the engine. The only possibility that is outside of the seized engine scenario is if the torque converter has become welded to the bushing in the transmission oil pump.

Now that's a relevant reply. Thanks.
For a few months now, she's been difficult to nearly impossible to push when supposedly in N.
I'll try again when I have 2 or 3 strong men available.
As for the the T.C. welding itself to the pump bush, I thought that MB switched from a bushing to bearing at some point.
Unsure of the year.
I do know that the current transmission was never serviced at all.

 

[toteimerced]

Unfortunately, is sounds like it’s seized.