Hello guys. Got a 2021 sprinter 315 MWB rwd automatic 9tronic Went for a holiday and came back the van won't turn on. Checked the battery and all fine. Got the AA in, he tried to turn on straight through the starter motor and nothing.Checked fuses from main box all fine. OBD reader says 6 errors, all connected to the ECU (photo attached)He said maybe a rat chewed some cables but I find it unlikely? Had a good look underneath and nothing seems out of order. The lights from inside the van had stopped working a couple of months ago, so thinking it might be related?Any ideas are greatly appreciated. Thanks

these errors look off the charts

​​​​​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...
🤞

Thanks for the quick reply!

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


​​​

Reboot done, checked all fuses, checked relays between 70/110..
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 🙏

There you go... you've landed where things went bad: the prefuse box.


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.

Just wanted to update in case anyone goes through the same, and big thanks for the help @CaliBenzDriver

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!

The last Benz specialist got your vehicle running when nobody else would bother poking it.

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.