Yazeed Ayasra

Dears

I am having a serious problem with apperently no solution, i tried posting before but no help

My check engine light is on and i get two errors

3548 the on - board power supply voltage is too low
0046 the boost pressure control flap has a malfunction

The mechanic replaced
1-the boost pressure sensor
2- the boost pressure flap
3- the engine control unit (ecm / ecu)
4- the battery
5- the cables and wires for the flap and the sensor were checked carefully! Nothing seems to be wrong

The issue went off for 24 hours after ecu replacement and returned back, the only symptom it has is that sometimes the compressor goes off and the car become very weak, it returns to normal when restarting it!

It did cost almost 3000$ with no results, any help would be highly appreciated

Alfadude

I'm sorry I cannot help you, but the first thing you should do is go back to the place that did the work and show them that the issue has not been solved.

It would also be helpful to know what exact year and model of W204 you have.

Yazeed Ayasra

Thanks alot for your reply, i tried many mechanics and they dont seem to be able to tell what the issue is, some of the parts were changed twice in more than one workshop and yet with no clue of whats going on!

Its 2008 C200 1.8L

Moto_Guzzi

You should not pay if problem is not solved, you do not have an experimental or tech training vehicle.

dol4er

Why didn't you go to the MB dealer in your city?

Yazeed Ayasra

yh i know but the check engine light goes off, i try the vehicle, push it to the max and it always seems that the problem was solved, i pay for it and in few hours it kicks back in, i cant return the parts i purchased because the parts store is not responsible for the mechanic fault and so on, still with no luck finding what the problem is, do you have any idea what does the "on-board power supply" because i don't think its a common error?

Yazeed Ayasra

MB in my country is uncooperative, i once sent a w211 that i own there for abs "factory fault free replacement" and they asked that i should remove all the after market parts and replace them with original ones, they sent me a quote of almost 10,000USD for my ABS free replacement !

Just204

the dealer said that or MB? I would laugh at someone if I was told that, they just wanted to get money out of you.

dol4er

I've always told everybody that, to my opinion, tricky issues can ONLY be solved by the dealer, no matter that it looks more expensive at first. In fact, visiting indie mechanics comes out to be much more expensive after the trial and error process and all the headaches after that.

IGB

And yet most on here (actually, on any forum) would swear by their level on satisfaction with independents...

dol4er

Sure... but that's my opinion. I'd gone through that trial and error process which turned out to be very expensive.

St0RM53

I had this problem, same 2 codes plus one about engine speed "the output signal for engine speed has short circuit to ground" even though rpm was showing correctly.
I replaced the boost control flap electronic throttle body but the problem didn't go away.
Anyways i was checking values in xentry and i saw maf was reading 0..wtf..i check no power there..i check fusebox and found n.22 15A fuse blown (looking online it's labeled "engine electronics"), replaced it and all fixed now. 0 problems, 0 codes.
It probably supplies the h-bridge for the ETB; i didn't open it to check if is shorted and blew the fuse..
So if you have this problem, check for the fuse first before spending money and pain to change it.

So i leave this solution for anyone to find.

edit: also mercedes has stupid error codes, design is very bad..it should give error for all sensors powered by this fuse but it doesn't..FAIL