Car shakes at idle and lots of codes

Avel Du

63,866 posts · Joined 2015

#2 · Jul 28, 2025

Mountain of issues.
Shaking may be engine mounts but you have so much more going on.

There is a thread somewhere on checking the engine mounts.

Now, codes.
Do they come back when cleared?
If they come back is it all at once, or a few to begin with.

 

BaD_81

7,377 posts · Joined 2019

#3 · Jul 28, 2025 (Edited)

I guess you used some OBD|| scanner, not BM diagnostic tool. Not saying is not accurate, but from time to time the “translation” between machines is not accurate.
And because of that, Errors from not MB devices are TO BE CHECKED first!
Full Diagnostic Trouble Codes List | Engine this doesn't mean the code applies for YOUR machine it is ALL MB CODES!


And here STAR TekInfo m112 motor details

That leads to:

And

Now these all are guidance for YOU to check.

You might feel lost, but unless you start, you will never advance. And never get to solve it! So start reading!
The above is ONLY on P- Powertrain
Ready for Chassis?

Manuals

What do you know:

Alternator is doing the job, but there is a DIODE block that gets FUBAR for many reasons and the voltage is all over! Or the brushes on the alternator are history…who knows! Need checking clicking on []23=>1.0 will show you what to check.
Finished with that, take the next and again and again and again…

Will say it again - lots of reading ahead of you!

Cross check each code and select the right way.

Your vehicle, your money, your safety, your choice.

If you get stuck, ask!

 

TomSLK320 Discussion starter

10 posts · Joined 2025

#5 · Jul 28, 2025

Thanks for the info.

 

TomSLK320 Discussion starter

10 posts · Joined 2025

#6 · Jul 29, 2025

I'm starting to think that maybe those codes aren't actual problems, but are just due to a battery disconnection or low voltage from the past, as I have never been able to clear those intermittent codes with my scanner.

Still don't know what could be causing the shake at idle, though.

 

BaD_81

7,377 posts · Joined 2019

#7 · Jul 29, 2025

Well,
Battery charged overnight is 1st.
Fresh Fuel.

Questions:
F Filter
Plug wires
Injectors
MAF

Can you share what is new, services, old?

 

DB007

9 posts · Joined 2023

#8 · May 8, 2026

The check engine light (malfunction indicator lamp) illuminated in my 2009 SLK 300 and several emission related codes were generated on my OBD-II Mercedes scanner. Changing a relay did not solve anything. Coincidentally, the engine developed a vibration that progressively became more severe.
Careful inspection revealed that one side of the engine had dropped about half an inch, since one of the engine (hydraulic fuid filled) mounts had collapsed. I replaced the engine and transmission mounts during which time I also moved some wires away from each other and from a heat shield on the passenger side of the engine, and some others away from the transmission while also changing the automatic transmission oil. This effort took me several days (with the car level and elevated on ramps and stands) during which time my 5-year-old battery slowly died, probably because I left the doors open inadvertently causing several lights to remain illuminated, and numerous electical codes then also appeared on my scanner.
After replacing the engine and transmission mounts with new ones, adjusting the wiring, and installing a new battery (and also changing the transmission fluid) all the problems vanished. No more fault codes, engine light remains off, engine runs smooth, passed the emission test, and driving the car is a dream!
I hope you or anyone reading my reply finds something useful here and wish you as much good fortune.