I think my shifter lever is malfunctioning
 

I can move it out of P to any other position, regardless of ignition key status or the brake pedal.

I've seen that there is a repair kit for when they get stuck in P. Is this the same kind of failure, or maybe something else?

Not a critical problem though, just strange. I'd hate to bump it into N by accident and step out.

Also, regarding the shifter knob, it has some play, I can rotate it slightly in either direction but I'd like it to be snug and sit straight.

Probably some plastic wore out on the inside and it would need to be replaced, but if anyone has encountered this problem please let me know.

Is the car going into the selected gear when the transmission lever moves freely?

There is a chrome ring on the buttom of the lever knob which secures the knob in place. It might be that that's lose

Yes it selects gear correctly, just doesn't require a break pedal to be engaged or the key position to be correct. Must be a bad shifter lock. I'm considering buying a used one to take apart and rebuild so I can understand how it works.

The ring locks it in fine, but once on it can just slightly rotate. There is a flat surface at the top where the keyless go wires connect, it should sit flat against it so I'm thinking maybe its worn out inside? Difficult to find a replacement so for now I'll live with it.

I currently have the entire center console out, rebuilding it due to all the broken plastic, replacing COMAND screen, wiring in a bluetooth aux. Its just about ready to go back in but maybe I'll delay a bit to see if I can get the shifter figured out.

It sounds like the shifter lock mechanism pin has broken. It's quite common and most of the times will result in the lever not getting out of park.

Being able to move between R<->D without applying the brakes is normal

It's strange that I can freely move out of P regardless of pedal or key, but it must be the same thing.

I decided I'm going to take it out and disassemble while I have the center console out anyway, don't want to do that twice since its so delicate.

Appears that the locking cable broke at some point and was simply sitting detached. But even with it in place, doesn't seen like it would stay in P, I applied pressure where it would've been but was able to move it around.

Going to get a 2nd shifter, I think I can grab a good one locally from a 2001.

https://cimg9.ibsrv.net/gimg/www.mbw...0b4c641c78.jpg
How I found it
https://cimg8.ibsrv.net/gimg/www.mbw...f271381402.jpg
Tape removed
https://cimg7.ibsrv.net/gimg/www.mbw...059c57c188.jpg
Metal housing is off. I thought there was supposed to be another plastic cover here? Found a rogue locking ring resting inside.

What I've learned is that the existing shifter was gutted to remove all interlocks and safeties, which is why it was also disconnected from the ignition lock cable.
I got a good shifter, swapped computers between the two, but it will not move out of P.

After a lot of testing and research, what I see is that the ESP module is unable to properly signal the stoplight switch status to the ignition module and the shifter module. It is logging CAN bus errors stating it can't communicate with EIS and with the Cluster. But actual value testing in DAS shows that it correctly detects the stoplight switch position.

I'm checking through all the CAN wiring now to see if I can find the cause. Possible that the ESP module itself is bad, seems like there are plenty on eBay and they aren't expensive so perhaps I'll swap it if all else is good.

In all my searching, I only found 1 thread on mbworld with the same error codes, it was from 5 years ago and was never resolved.

Errors in ESP:
C1034-000 CAN communication fault with N73 EIS/EZS
C1043-015 CAN communication fault with A1 Cluster
C1200-008 stoplamp switch plausibility

I've seen some writeups about calibrating the stoplight switch, but saw nothing like that in WIS so I'm not sure what that's about. There is also a Star Bulletin which says if you see these codes, pull fuses 29 and 30 from the pass-side SAM. I don't quite undertand this approach, it just made the ESP state that it can't reach the ME. That document is P-B-43.45/74.

Looks like the gear selector module doesn't have continuity on CAN-C, other modules were fine. These are the green and green/white wires.

I'll need to rig up some test wires now, then if it works I can run proper new wires and solder them to the junction points in the driver footwell.

Despite testing as Good, the stop lamp switch turned out to be the problem after all! I replaced it and then the shifter unlocked, so now the interior is back together after a while, and I have a spare ESP module from eBay now.

The other CAN errors seem to be irrelevant, don't cause problems, and don't show a warning light.