sAMGih

Hey guys,

I just got a 2009 C63 AMG with around 35K miles. The car seems to be in great condition. The car needs service A, but I knew that going into the deal, the seller agreed to pay for anything else that was discovered during service A that was beyond the usual amount for Service A ($350), and I trust the seller.

What was disappointing is that after 1 day of driving I got the Engine Malfunction yellow light on the dash. I retrieved the codes and they are: P0171, P0745 and P2091 (see attached screenshot).
The last 2 are not marked as "Current Fault" by the Torque Pro app, so I'm not sure what it means. Screenshot attached.

The seller gave me all service records for the car and I don't think he ever changed the intake manifold gasket, which is commonly associated with P0171.

Does anyone have any advice? I'm really loving the car, it's driving very well and I hope this is not a huge issue.

Thanks.

whoover

P0171 on this car is often the head bolt problem. See the sticky topics above.

Jons95c36amg

No its not. I have no issues with headbolt. I get this same code P0 171 when I remove the charcoals.

BD-C63

I had this issue and they replaced the gas cap, but it ended up being a sensor on the engine. I can't remember which sensor it was though... No biggie if this is what it is.

sAMGih

Now that you mentioned this, I've read about the head bolt problem... Apparently it takes 3~4 weeks for a dealer to fix it and it costs something around $6K. I don't think this is related but oh man, what have I got myself into.

BD-C63

Don't stress out about the headbolts. In my opinion it is a very rare occurrence but it has been blown out of proportion on the forums. The check engine light is typically emissions related so there are a lot of minor things that it could be... I've had my 09 for over two years now and it is by far the best car that I have owned!

estrellajon

P0171 is a lean code. Worse case it's intake manifold leak. Easy fix. Or air box not secured properly or charcoal filters missing .

sAMGih

Thanks, I will go for Service A and will have the engine warning checked.

tfthach13

The intake manifold leaking is most likely the culprit. I had mine fixed while it was under warranty. Not sure how much it would be post-warranty.

Side note: I feel like leaky intake manifolds become more apparent (CEL codes pop up more frequently) with charcoal deletes and/or aftermarket filters. Since I had my gasket replaced, my high-flow filters never gave me a CEL, whereas before it will pop up every once in a while. Can anyone confirm this?

avery.whss

it's not the intake manifold, i highly doubt it, CEL never even came on when I needed my intake manifold replaced, purge valve needed replaced - Again no CEL and it was stuck open, O2 sensors - again no CEL but needed replaced, and my car STILL runs lean bank 1&2, no one on this forum or at MB has a clue why, i even put my car back to 100% stock, CEL came on, so these cars can have a CEL come on for 0 reason infact, i've given up on trying to get rid of the lean code..screw it lol ..car runs fine anyways

moral of the story OP, never trust a computer, they lie sometimes

Merc63

Lean code means there is a leak PAST the MAF sensor.

avery.whss

not for me, brand new MAFs and airboxes, MB's checked all the hosing etc

dubzAMG

Did they check fuel trim numbers, or smoke test for leaks? As Merc said, p0171 is bank 1 system lean, which is unmetered air AFTER the mass air flow sensor.

abcut973

your case is unique

As for OP it is not the headbolt issue. Get it check when doing service A or diagnose it your self if you are a DYI person.

gmurad

Hey, how would I start diagnosing the problem? I saw some videos on YouTube of someone spraying the engine to find leaks, and when a leaky spot was hit by the spray the engine would rev up. Would that be a good start?
What else could I do?

Thanks.

estrellajon

Correct. Use a MAF or throttle body spray to identify leaks if any.

gmurad

Hey guys,

According to the shop that I took the car to, the problem is either an intake gasket leaking or less likely it could need an entire new manifold.

The shop will first try fix the intake gasket leak ($423.44 including parts and service) and if that doesn't fix it she said it would need an entire new manifold.

Does this diagnostic seem sane? The original problem was a CEL (P0171 - System is running too lean).

avery.whss

i replaced everything the MB techs told me to when I got that code (still have it) .. 6 months later here I am, still running lean, so screw it, car wants to run lean let it ..I've prob spent 7k (intake manifold, purge valve, A/F sensors) on trying to figure out the problem..all I'm saying is, don't be surprised if MB comes back saying they have no idea whats wrong after they replace everything that could cause it, because it happen to me..I'm guessing you're bone stock? I put mine back to bone stock and they still didn't know what was wrong,

To be honest I don't trust a CEL period, it's triggered by some retarded computer that sees 1 thing off and fires out the code, my intake manifold whistled like crazy and it never once flashed CEL but it flashes CEL over a lose gas cap? Lol..Gas cap is like $50, intake manifold is $5k here in canada

Diabolis

Those are two possible causes, but certainly not the only ones that could throw a "bank lean" code. It would be a good place to start though.

SROC276

had that code and P2179. Intake manifold gasket replaced and now they are replacing upstream (driver side) o2 sensor because it wasnt reacting as fast as it should under normal cycle. Hopefully this will fix my issue.

Autosport7

This one word in your plethora of explanations scares me when it comes to car knowledge. Sorry... Just sayin.

roadtalontsi

they just gave up or what? stock tune?

not trusting CEL lol, come on man. You'll kill your cats, spark plugs, possibly the cylinder walls/rings - wash them down with extra fuel.


Saying a lean code has one official cause is very vague. Yes in most cases on the m156 it's intake gaskets. Lean codes occur whenever oxygen sensors - see the name OXYGEN - read too much oxygen. It has nothing to do with detecting the amount of fuel at all. The reading is strictly measuring oxygen content. If you have a misifre (poor ignition/burn) unburnt fuel and unburnt oxygen (sees too much oxygen) throws LEAN code. vacuum leak - extra oxygen that wasnt metered causing a bad mixture - throws lean code. It's much more complicated then ya'll think.

avery.whss

yeah TIPs canada was involved also and they have no clue, MBs checked the car out and it's fine actually, just for some reason it fires the code , they checked everything, replaced everything that could be replaced related to it, and still the same code comes up, I don't trust it because my intake manifold whistled like crazy and never once did CEL come on, but yet I leave the gas cap loose on acident and the car screams at me lol , same with the purge valve, no code or CEL and it was stuck open ..is it possible my ECU is whack? MB suggested replacing it as a last resort