ECU communication error





ECU faults basically mean "bad module". All by itself no collaterals causing that??
Do a power cycle with all battery GND disconnected... a chassis REBOOT to see if that helps cut down on troubleshooting.
The hope would be ECU missing power from compromised SAM relay... Is this high mileage/delivery high crank-count that could explain bad relay???
"Lights stopped working"... that's definitely a good lead to go after chassing right from fuse box.
Remember always go to the obvious basics first before getting super fancy first. Check power
Do you have decent battery charge/voltage ?
These chassis have multiple ways to drain...
🤞
Last edited by CaliBenzDriver; Jan 19, 2025 at 11:13 AM.
No collaterals apart from 1 month without being switched on and a bit of cold days (one snowy weekend).. maybe the cold triggered something?
The van has 60k miles and was owned by a motorway contractor, so it had tons of earth/dust when I got it, and I did clean it so might have messed something up when I removed the front seats?
Battery voltage is good
Will follow your recommendations,
Thanks for that


ECU faults basically mean "bad module". All by itself no collaterals causing that??
Do a power cycle with all battery GND disconnected... a chassis REBOOT to see if that helps cut down on troubleshooting.
The hope would be ECU missing power from compromised SAM relay... Is this high mileage/delivery high crank-count that could explain bad relay???
"Lights stopped working"... that's definitely a good lead to go after chassing right from fuse box.
Remember always go to the obvious basics first before getting super fancy first. Check power
Do you have decent battery charge/voltage ?
These chassis have multiple ways to drain...
🤞
I've removed the drivers seat and is pretty nasty around the fuse block 150/4
I've noticed that overhead controls aren't working either..
All fuses are good tho, battery is good.
Will give a good clean in the fuse block and see how it goes.
The led module sparks a green light when I try and start the car so there's current going into the led module
Also noticed loads of cables for trailer so guessing you are right about high crank 😅
Any ideas are really welcome
Thanks 🙏
Last edited by Gabs; Jan 21, 2025 at 07:41 AM.




questionable hot/wet/oxidized MAIN connections....
-- Its very appealing to clean it right now BUT BEFORE DISTURBING anything... do the right troubleshooting.
> go ahead and pin point where/what power connection is bad using SCHEMATIC diagram.
You know a collection of circuits are bad.... trace where all these circuits source power....
> then measure live voltage drop or missing voltage
then disconnect batteries for electric surgery repair.
Last edited by CaliBenzDriver; Jan 21, 2025 at 02:03 PM.
Finally managed to get a willing auto electrician in, he plugged his "mercedes" obd and the codes read as per picture attached.. basically there was no power going to the ECU and it could only see 16 out of the 22 computers from the van..
After a lot of back and forth and nearly giving up he opened the bonnet and started twitching the ECU cables whilst I was trying to start the van.. and presto! It fired up
Basically the wiring is damaged and by moving it around he managed to get some contact
The first auto electrician I called didn't even wanted to come over as he said ECU problems are dealt only with Mercedes.
Hope that helps anyone that faces same issues as me!
Cheerio!





guided troubleshooting
I can only hope he found out why fuse box was cooking poor connections.
burning hot oxidized voltage drops
There's something that needs to be learned right there...
Keep your batteries well charged to defend against "drained by parking".
Never rely on ALT to charge flat batteries with extreme current that will burn up harness connections.

Last edited by CaliBenzDriver; Apr 4, 2025 at 03:06 PM.


