When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey everyone, I’m at my wits’ end with this car. My 2009 Mercedes C200 Kompressor has been throwing a P2187 (System Too Lean at Idle, Bank 1) code since October, and I still can’t figure out the issue.
Here’s the freeze frame data from the latest scan:
Short-term fuel trim (STFT): 5.47%
Long-term fuel trim (LTFT): 0%
Intake manifold absolute pressure (MAP): 4.93 psi
MAF air flow rate: 7.41 kg/h
Throttle position: 12.5%
O2 Sensor 1 Wide Range Voltage: 2.01V
O2 Sensor 1 Equivalence Ratio: 14.73
Fuel rail pressure: 55.1 psi
The car idles fine but has rough starts and some hesitation. No major drivability issues (yet), but the check engine light has been on for months, and I just want it gone!
What I’ve tried so far:
✅ Replaced O2 sensor (December) – CEL was already on before, and this didn’t change anything.
✅ Replaced MAF sensor (2 months ago) – CEL was already on before, and this didn’t change anything.
✅ Looked for obvious vacuum leaks – Nothing obvious, but maybe I’m missing something?
At this point, I’m begging for help 😩. Could this be a vacuum leak? Fuel delivery issue? Bad O2 sensor? Something else I haven’t thought of?
Before I throw more money at parts, I’d love some advice! Any help is seriously appreciated 🙏
Not sure what engine that is. Im only familiar with the M272 which I dont think you have.
I would remove the air intake and inspect everything, inspect pcv hoses, air box seals, all rubber hoses etc. In the manual for mine it says even a cracked air box seal going to the maf can cause faults, unmetered air getting in.
Is your engine M271.942? That’s more like the W203 engines on this site. You may get more replies by reposting there.
I’m also not familiar with specs for that version of the M271, but that fuel rail pressure would be low for M271.8xx. Is the fuel system SFI (port injection) or is it DI (direct injection)?
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
