I have a W222 S550 2015. All was fine until last week. Then the ignition stopped working, xentry showed nothing on the interior CAN, expecially front SAM.

Also circuit 15 is not switching on, relay is fine and it seems to have voltage.

Next day everything was fine again, all units reappeared in xentry, lasted 3 days then same problem appeared, Im guessing some kind of loose connection or bad ground, I've checked eveything I can think of.

The ignition EIS unit, controls the interior CAN. When I put a meter on the CAN lines (with all CAN units disconnected apart from front and rear sam) both high and low show 2.5 volts dropping to 2 volts every 4 or 5 seconds. I think its trying to handshake but not getting anywhere.

Ive been through all the wiring diagrams, checked every connection that I can see. Still cannot solve it.

I notice when I manually close the circuit 15 relay, the can CAN voltages stabilise imediately and all the interior power comes on BUT neither front or rear SAM are recognised. I've tried changing both SAM modules makes no difference.

Does anyone have any experience troubleshooting circuit 15 or interior CAN. I'm thinking fixing the circuit 15 will automatically fix the interior CAN but I could be wrong.

any and all advice gratefully appreciated.

 

Finally solved it, took a few days. Here’s the steps I took.

I checked every wire coming from front SAM (over 50 of them) for continuity, short circuit and open circuit. Also checked all wires related to circuit 15.

Swapped out the following

Rear Prefuse box

Rear fuse and relay module (inc all relays)

Drivers side fuse and relay module (inc relays)

Engine Fuse and relay module (inc relays)

EZS Ignition module (as Internal CAN originates from there)

Front SAM

Rear Sam

Disconnected all other modules from the Internal CAN Bus

I also disconnected every other module that connected to the front SAM just in case one of those was faulty and knocking out comms in the SAM

Nothing made any difference

At this point I was totally stumped. It now seemed obvious that the front SAM did in fact control circuit 15

Went over everything again, if all wires were OK and all modules were OK what was I missing?

There were only 3 things I had not checked, 3 Can Bus Distributor blocks. There is one in cockpit area that only the SAM, Climate control and EZS Ignition connect to

There was one under left drivers seat carpet and one under right drivers seat carpet.

I 'borrowed' them from a similar W217 coupe that I have. Hooked them up and lo and behold, everything came back to life.

Checked a bit more and it was the one under the right seat that had gone haywire. It is the only one of the 3 that also has a ground connection (I had checked the ground connection and checked it for shorts at the beginning.

I did some research and discovered that these distributor blocks have 2 x 120 Ohm resistors in parallel and if working OK should show 60 ohms across can high and low when tested with a meter.

The faulty one had a ready way off the expected 60 Ohms, clearly had suffered some kind of internal failure.

The new blocks were less than $20 each so I am replacing all 3 just to be safe.

Hope this helps someone in future. Picture of the affected CAN Distributor block attached.

 

This is the white block, correct? I'm having a similar issue but not with a W222 and the car starts fine. I get Circuit 15 off is implausible. U301100 code.

 

Yep, its the white Canbus block. Its only about 10 bucks

 

Is this what cause your electrical problem.

i have 2007 cl550, when key put into ignition it turns light up like a Christmas tres. Just like this. Key won’t lock or unlock, windows won’t work, key functions won’t work. Don’t make sense I need help