Electrical woes

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MB Enthusiast
May 19, 2006
Deepest darkest Zummerset
C207 E350 CDI coupe
2009 E350 CDi (W207)

For a while now i've had issues and am now reaching the end of my tether! Basically the car will intermittently fail to start when the key is turned, displaying "ESP inoperative/Abs/run flat" in display. Solutions to this generally involve multiple restarts, sometimes it needs codes cleared and then will start ok.

interestingly, locking and unlocking works well.

Apart from this it drives beautifully with no warning lights etc..

I have been working through potential issues with a mechanic friend... various things including
-resealing boot as rear SAM had got a bit wet through leaking seal. SAM was ok but a few wires were chafed on boot lid so those were repaired
-we repeatedly got a Relay 15 fault to the extent that car completely refused to start. Recently sen5 off EIS to be checked, which was OK, so ESL was replaced with an emulator. This has improved things, but fault remains.

The final thing ive tried is replacing the brake switch. Faults remain. This is the most recent diagnostic print:

Any thoughts? The faults seem so diverse that i'm starting to think an ECU fault might be present.
Theres nobody local with STAR although this may be next port of call.

Failing battery .?
I'm now wondering if the EIS was actually OK after all. Just in the car now and first turn, no crank. Remove and reinsert key, starts straight away! There don't seem to be any other variables.
With all those separate faults I would be looking at the canbus to check both sides are ok. If it is being pulled down it can be tricky to find where the damage is but at least you would know what you are looking for. Saying that a good diagnostic session on star with someone who knows how to drive it will probably save you money in the end. That’s what I would do but I’m lucky as there is a good local Indy.
Thanks Andrew, that is going to be the next step, have it booked into Indy in Bristol. Wanted to exhaust every possibility myself locally as i have a feeling this might be painful!

My auto electrician mate stated that the wires in the boot have been worked on before.

Slightly annoyed steering lock hasn't sorted it, but only £100 down.
This car continues to pain me!

Car was booked in at specialist, however for 2 weeks it was absolutely fault free... started perfectly all the time. Took it up anyway, they couldn't find any faults on STAR.

Now back to its old ways! Specialist has said if its booked in, first thing will be a new Merc steering lock, so £400ish down.

interestingly, the lock thats come out is dated 2016 so its been replaced before!

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