I might add that I have what many online retailers are calling "camshaft locking tools" - which in my opinion are really just camshaft "hold down" tools (for use with the cam covers off, since the cam covers have integrated bearings.) I can't seem to see any way that these tools would have the ability to "lock" the camshafts, and certainly not index them.

 

Also, if anyone knows any techs well versed in the M276, happy to pay for some advice. Thx!

 

perhaps the reluctors are NEVER supposed to move

Yup. You have bad camshaft. Replace the camshaft, the reluctor is not supposed to move at all. Unfortunately MB cheaped out and had the reluctor pressed in, instead of welding them.

 

One quick look at parts footnotes. Same footnotes for exhaust cams. Things are messed up.

 

Thanks so much folks. Does that mean there’s no real way to verify if the same problem might be on the other three cams?

 

Not really. Ideally you want to replace all four cams.

 

I hardly think that at 220k miles, I'd describe any type of failure as "cheaping out". At this stage, I'd replace the entire timing chain and associated parts.

 

agreed, at 220k miles, I think my reluctor wheels would start slipping too Thanks to all for the guidance!

 

Mercedes is just garbage, I have a ML 350 with 55k miles, same problem. They are genius designing the worst cars in the world

 

I am very late to respond to this discussion but I will offer this: I am helping a friend fix his daughters car. 2013 E350 M276 won't pass smog. On tear down I found the reluctor wheel or Sensor wheel on the camshaft had moved slightly on 3 of the 4 cams. I initially thought of moving them back in place and placing a roll pin to hold them from moving again. Second thought, and what I did, was to drill a small maybe 1/16 hole in the reluctor plate just deeper than the thickness of the plate barely into the cam, after moving the sensor wheel back into the proper position, both lines matched up. Now I spot welded my drilled hole. This serves only to keep the sensor wheel from slipping and moving on the shaft. To move now it needs to move over the spot weld hump and break loose from the spot weld. There is no force trying to move the sensor wheel. IF you keep it from moving it will stay put. The spot weld is tiny, less than 1/8", does not interfere at all with the cam adjuster on install. There is a lip around the sensor wheel that locates the wheel on the camshaft facing forward to front of engine. I drilled only in this lip, it is about 1/4" wide. Placed my ground for the welder very close to the actual weld to avoid sending voltage elsewhere in the engine while welding. The spot weld is a 1 or 2 second touch weld, finished it is not much thicker than the Sensor wheel lip. No extended weld time that builds heat. For me, it worked, I did this to all 4 of my friends cams. I wish I had this thought to do this when I replaced the cam adjuster on my E350. When the cam adjusters fail they bang on the shaft, I believe this banging is what makes the sensor wheel move on the camshaft. Note the photo Juanmore added below shows the cam sensor wheel and you can see the lip I drilled and welded in the photo, it is just press fitted onto the camshaft so a slip fit if you will and the slip fit is not tight enough to avoid movement. FYI: I bought the tools pictured in the photo, it was still pretty vague to me so I ended up setting up the cams as I thought they should be and then dropping the valve cover with no sealant yet applied on to the engine put most of the cam cover bolts in place till the cam was fully seated and checked the cams from the cam sensor holes to verify before sealing up the cam covers. You can't do this wrong or you will waste 10 hours time so it was worth taking 30 minutes to verify before assembly.
Hope this helps someone else.
EDIT: When you look at the cam alignment line and the cam sensor wheel line, they are etched in the metal and hard to see. Make sure they line up dead on. A very small mis alignment at the shaft is a large mis alignment at the outer part of the sensor wheel where the cam sensor reads it. So what looks close enough at the center might move your wheel 5* on the outer wheel so pay close attention to the lines when checking. You cannot see the lines till the cam adjusters are removed in my experience.