Jeff Ostroff

Our 2013 C250 (W204) started knocking a bit while driving the other night, felt like the engine would bump slightly every 10 seconds or so, then check engine light came on.

I use the Torque App with my OBD2 reader via bluetooth, and it passes the scan with no issues, but on my phone the Torque app kept showing an old "Historic Fault" code P0303 which is the dreaded "Cylinder 3 misfire" fault. But this fault was in green, not red, so there was apparently no present engine fault. Yet why is check engine light on?
99% of time it's the spark plugs, so I installed new spark plugs, torqued and gapped per Mercedes spec.

PROBLEM: When complete I told the Torque App to reset the engine fault code, and it said it was complete, but the check engine light never turns off!

So then I tried an older OBD2 reader that I have which does not talk to the phone, you just press the red button and it resets the ECU. I tried that and it too said on the tiny LCD screen the message was sent to the ECU to reset, but the check engine light is still on!

I tried this with the engine running, and without the engine running, nothing works.

Why is this check engine light stuck on, and yet not showing any faults? I have never seen anything like this before, usually where there's a check engine light on, there's a fault code not far behind.

xsever

Maybe the nature of the error code cannot be reset with a generic OBD2 reader and requires something more specific to Mercedes. I do have an OBD2 bluetooth reader, but I also bought an iCarSoft MB II so that I can reset all codes. A good example of this is Transmission Control Unit (TCU) errors where some of them cannot be reset with a generic OBD2 reader whereas an iCarSoft MB II can.

Jeff Ostroff

That is so messed up I don't see why in the world they would require something else to reset that code

Jeff Ostroff

Well things just turned a little stranger hopefully for the better. I got in the car this morning to take it over to a local repair shop to see if they could clear the check engine light since I don't have the proper scanner to clear the Mercedes ECM faults. I started up the engine and there was no check engine light anymore so perhaps the engine ECM took care of the fault upon its own, after I changed the spark plugs. So I did not bother going over to the shop I am just hoping that this is not an intermittent mystery issue I am hoping the light stays off.

5by5

Good to hear the CEL resolved. Funny you couldn’t reset with Torque/obdii or generic scanner. I’ve never had a problem clearing codes with either one except for SRS codes.

Off topic question for xsever: do you recommend the iCarsoft? I’m maintaining 3 C-class cars and wondering if I should go iCarsoft or mess with a third party STAR system. It seems that the iCarsoft would be cheaper and more convenient to use. Do you have any issues or regrets with it?

Anyone else care to make the case for STAR? I’m weighing options...

Thanks!
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xsever

I still have the C3 STAR back from when I owned the CLK, but it doesn't work with my 2012 C300 so I had to get an iCarsoft. I am therefore able to give a good comparison. The iCarsoft is suitable to read codes MBZ specific codes, reset them, and read live data. It cannot do more advanced stuff like adaptations and such. For the $130 I paid for it, it does the job. Mind you I haven't run into any serious problem with my car given it's extremely low mileage.

If you are maintaining 3 C-class yourself and plan on keeping them for long, and if you plan on buying Mercedes cars in the future, it would definitely be beneficial to invest in a STAR system.

Jeff Ostroff

So what makes this carsoft able to d stuff that the OBD2 reader that I used can't do? I was surprised to find out our standard OBD2 reader did not reset, and makes me wonder if it reads all the faults correctly, because there was no red colored fault.

xsever

iCarsoft produce manufacturer-specific diagnostic tool rather than the generic OBD2 protocol.
This is the one I have. You can read all about it: https://www.icarsoft.com/Product/s-3...oft_MB_V2.html

5by5

Not sure I can afford/justify the C3/C4 STAR. The hacked ones are out there but they sound sketchy. Not sure the hacked C4 version even works anyway since it needs to communicate with the MB database via internet.

Autel DS708/808 is sometimes listed as an affordable “in between” solution. Anyone have experience with them? Website says you can do programming but not sure what they mean.

i have a lower priced Autel generic scanner that was somewhat disappointing. Reads codes and data ok but not really any better than obdii/torque.

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