This procedure applies to all M112 & M113 engines and is a common solution for stalling issues.
As M.B.DOC says:
"The most common problem on the 1998 & later V-6 & V-8 (M112/113) engines that will leave you stranded is the crank flywheel sensor. WE replace 5-10 a week at dealer."
Since no one volunteered their expert advice on the crankshaft position sensor (CPS) DIY, here it is...hopefully this will help others with what appears to be a common stalling issue in the ML series.
I checked NetStar for PO work (done under warranty) and learned the fuel system mod had been done at 29k (now have 48k). So I figured the stalling issue wasn't that. I may be wrong, the CPS was cheaper place to start!
I give this job a 1 to 1.5 stars (of 5) difficulty, and maybe a 3 stars for patience.
Here it is:
1) Get a CPS, its a VIN specific part. $125 from my local dealer.
2) Tools needed: Socket screwdriver, Good lighting (portable) shop lights, size 8 outside torx socket, maybe a ratchet and extentions depending on your flexibility, magnetic part retrieval tool (skip this at your peril), bath towel, and long sleeve shirt, step stool, blue thread locker (optional)
3) Open hood and remove engine cover, it just pulls off and on
4) Set work light(s) toward back of engine, lighting behind drivers cylinder head
5) Set bath towel on front of ML to kneel on of your knees will die, wearing long sleeve shirt or your wrists will be cut.
6) Climb up on towel and look behind engine from above and right, finding torx attachment holding your CPS.
7) Remove torx screw and pull out CPS, disconnect one way connector (wiring)
8) Replace with new (leaving wire detached for now)
9) This is the hardest step by far, and requires patience and flexibility. Apply some thread locker and insert screw and start the threads. Tighten with torx on socket screwdriver. This step took about 1/2 hour and numerous dropped screws and retrievals with mag tool. A tip that makes this much easier is to put bearing grease or something similar in the torx socket, this will hold the screw.
10) Attach wiring to CPS
11) Reinstall engine cover
12) Clean up tools, towel and lights and everything
13) Drink beer and toast yourself for saving yourself at least $100 and a day of your time dropping off and picking up cars at shop
Hope this helps someone in the community.
To answer a number of Qs, here goes!
1) It did fix the problem. No stalls since changing out CPS.
2) I should have noted, though it is stating the obvious, is that I would only do this on a COLD engine.
3) No resetting of anything required (as far as I know), as the engine was off and its not a vehicle/VIN specific part in terms of absolutes, just a range of VINs (and maybe 320/430/500 specific). The dealer wanted the VIN to make sure he gave me the correct one. I am not sure how many variations there may be, I did not ask.
4) It is on the back, drivers side of engine, where the engine/transmission mate up. Its kinda a PITA to get at. I purchased the part before I started so I knew what I was looking for. The external torx socket is difficult to see, but you can do it. Good lighting is essential or I don't know how you would find it.
Discuss this DIY here.