W204 350CDI Dead, Advice Please

Page may contain affiliate links. Please see terms for details.


Active Member
Oct 2, 2017
The Titanic
Hi All,

If anyone can give me a little insight into what may be wrong with my car that would be fantastic.

I have a 2010 W204 C350CDI

Yesterday on my way home it just cut out and I had to coast to a stop. Upon trying to start it again the ignition would light up but not crank, I was recovered to home when I went to scan it using Star but just my luck my unit has thrown a fit as well.

I managed to get some codes off using Autocom if anyone has insight into what may be casing this

11EC Starter control short to ground

11F1 Intake ait temp sensor, left signal lower limit not reached

11F2 Intake ait temp sensor, right signal lower limit not reached

11f5 Intake ait temp sensor, left signal too low

11f6 Intake ait temp sensor, right signal too low

120d Charge pressure positioner short to ground

1215 inlet port shutoff short to ground

As these are permanent codes i am unable to clear them until i identify the fault, but without star i am struggling to diagnose it.

Earlier to day I had noticed a buzzing coming form what seems to be the glow plug relay (this was replaced a while ago), I left the ignition on for around a hour and when I cam back to the car it was completely dead and the battery drained, whatever it is seems to be a short to ground.

I have checked the starter relay and that seems fine as is the fuse (fuse 20 and relay M)

Any and all advice would really be appreciated, thank you in advance
Hi. Why eould you leave ignition on for an hour?
I would be looking at ground wire to ecu or fuse box.
I hadnt realised I had to be fair, but either way it shouldnt have drained tbe battery.

I will check fuses for a short to ground, thank you
Did you check all other fuses, M55 may have blown one... but if glow plug coil light comes as it should, minor fuse should not prevent starting. I can't remember where big main fuses are in W204, find and check the,

Star motors sometimes break out of the blue...
OK so now taking a step back after my not thinking straight yesterday.

Fuse 24 blown, all I have for this is engine electronics, does anyone know what it's circuit is?

Checked all fuses in the engine bay for a short to ground and they are ok.

I get a momentary resistance reading on the engine electronics fuses the get open loop on the meter.

Slowly disconnecting things now and checking again
Seems I have a intermittent short to ground on fuses 26/27.

I need to find the circuits they are responsible for
Try unplug your swirl flap motor.

Hi it already is unplugged, along with the glow plug relay still get the short, wil unplug all the glow plugs, boost sensor and mafs to see if my short goes.

I have my star scanner working again (I think) although can't scan it until my battery charger arrives
OK so.

Fuse 24 and 27 go to the CDI Control unit, and 26 to Comand.

Not sure this helps me much although I am not adept at reading WIS if anyone has anything to enlighten the possibility
'Charge pressure positioner' could be turbo actuator... try unplug it ?
After checking all ecu pins for a short to ground pin 40 is shorted which i think goes to the oil level check switch.

Pins 2/4/6 also go to ground but are power from what I can see.

Woudo a old switch cause a problem like this with no warning light, or is that switch meant to be grounded and goes open when there is a low pop, my oil is fine not low.
OK much closer to starting now.

Got my charger so was able to scan the car, spurious errors everywhere cleared those down and replaced the blown fuse.

No errors on the scan now, not enough power to crank it yet but it does try, need to let the battery charge and fingers crossed.

If it runs I still need to isolate why it blew the fuse. My gut is the shut off motor. Will do some output tests once charged up
Think I may have had a injector short out blowing that fuse.

Found two leaking Injectors and carbon(black death) all over connectors, head and return pipe.

New pipe and seals ordered, will cutnteh seat faces and sort them, hopefully that's my issue.

Car now starts OK, it really is true without Star on a Merc you struggle diagnosing anything the dtc off other systems don't seems to be right and clearing codes isn't reliable without Star either.
Quick update to this.

It seems the root cause of fuse 24 blowing is the Intake Shut Off Motor.

I left it running on my drive once faults cleared and fuse replaced and after 10 mins it shut off fuse 24 gone again.

Unplugging the shut off motor the engine doesn't stop and fuse 24 is OK, problem found.

As a temp bodge to keep me going I used the resistor mod to stop the open circuit error and have a new motor incoming today. It doesn't seem very oily so hoping tbe intake isn't coked up.

Yes I had leaking injector number 2 but that wasn't the cause, I have replaced all seals and stretch bolts on that bank to be safe.

I will do the other bank again to be safe, those stretch bolts are not nice keep waiting for them to snap, all good though I made sure I used original Merc ones.

Anyway to keep it short in my case dead car with fuse 24 blown is a bad shut off motor (M55).

Hopefully this will help somebody else
Looks like I also have 2 X leaking injectors less than 5k miles after shelling out £1800 to get the oil cooler seals / intake manifold replaced.
Is it worth doing all 6 as I am told it's 5hrs labour and most of that is to get to them in the first place ?
I did all 6 of mine in a couple of hours and that included me running them through the ultrasonic bath

It's really not a difficult job and even buying any tools you need and parts will be way cheaper than you have been quoted
Thanks, I don't fancy doing it myself incase of snapping one.
It's a shame as the indie is local - guess I'll have to ring around.
Not sure, I was just told it takes a long time to get to the injectors.
As said, 5k since a big rebuild, how long does it take for a seal leak to gum up badly ?

Users who are viewing this thread

Top Bottom