W203 as of 03 were a mixed bag, they used EIS from a W211, same with ESL. It literally depends on what options the car came in with, as certain 203 will be optioned with a different type EIS/ESL because of a certain option.
This was before the front SAMs could actually have more options beyond certain codes.
Those green and brown wires are absolutely critical. They are the CANBUS wires....how do you think the EIS communicates with the ECU to start the car? It's through the green CANBUS wires. Brown CANBUS is the powertrain system, i think. If those are disconnected, no communication, no start.
Ok so as far as the CANBUS wiring, I have checked and replaced literally everything up front dash wise. So instead of the hacked together initial harness I tried (which honestly should have worked as I did it correctly in my opinion). I then replaced the dash harness with one out of a 2005 W203. I didn't think it would work anyways as the wiring ended up being rather different (CAN bus wiring completely different, but the EIS and ESL harness was correct which is why I attempted it). No difference with anything.
Next I pulled another harness from a 2003 W203. This ended up being identical to my donor C32's and what I am certain needs to work. So I installed that and... nothing. Still does the same exact stuff. I pulled the front SAM's from the 2005 and 2003 and tried both. One peculiar thing of note was that when I first installed the 2005 SAM when i tried the remote the door locks worked. Then as soon as I tried the key in the EIS, locks no longer worked anymore. Also currently neither of my instrument clusters show the shifter position. The cluster also does not turn on until the second key click (it should turn on at the first click). Something *may* be corrupting the front SAM's. I also checked the power distribution block fusible links and all visible ground points I could see under hood and with dash and front carpets off.
I tried using Xentry to help a bit but I don't have a good enough cable quite yet, either way I don't think it's going to be much help at this stage as the car sees none of the control units (my setup for Xentry works on my other cars). I have attached a picture that illustrates this. Doing a CAN test isn't even possible as the car doesn't even see the EIS. Bummer.
SO, I think it *is* a CAN issue of some sort and I have to have a short to ground somewhere? What does this mean? Going to have to do what I was dreading... I think I'm going to pull the entire interior to check all wiring in the car, will go ahead and replace rear SAM too (hadn't replaced it at all yet).
Before that I'm planning to put all my wiring and modules back into my donor car and see what happens just to test and see if I have a solid basis to work with even. As long as all the modules can interact with each other I figure the fault can't lie within the stuff I've already checked.