Hi guys,

I'm working through a rich running issue on my C63 AMG (M156 engine) and was hoping for some advice or insights from anyone who has experience similar problems.

I'm currently dealing with two fault codes:
P2188: System Too Rich at Idle (Bank 1)
P2190: System Too Rich at Idle (Bank 2)
Symptoms include noticeably rich fuel trims at idle (STFT and LTFT both negative), but the car seems to run fine under load. Here's what I've done so far:
MAF sensor has been cleaned, and readings are slightly high at idle but seem normal at higher RPMs.
Oxygen sensors are functioning normally, with expected fluctuations pre-cat and steady readings post-cat.
Given the rich condition only occurs at idle, I'm starting to suspect the EVAP purge valve might be stuck open, allowing unmetered fuel vapors into the intake. This would explain the rich mixture at low RPMs, where the engine is most sensitive to extra fuel.
Has anyone else had similar issues with the P2188/P2190 codes on their AMG? Would you recommend focusing on the EVAP system or is it worth digging deeper into the MAF sensor?
I'm currently running an EVAP system test with my OBDII to confirm the purge valve is functioning properly. Any tips on what to watch for during this test?
Appreciate any insights you all might have!

Hey did you ever solve it? Having same issue. Injectors are new, sparks are new, no leak at the manifold gasket, MAFs seem fine. Everything sealed and seated correctly.

idling jumping from 500rpm to 700rpm. Under load everything is fine.

P2188 & P2190

Did I solve the P2188 & P2190 issue? Yes I did........eventually. I did almost the same as you. Replaced injectors. Was just about ready to buy 2 new MAF sensors at $400 each but didn't. I did find a small air leak at the intake. Plugged that but still didn't go away. Finaly a friend of a friend told me to replace the "Fuel Pump Control Module". So I ordered one, installed it (5 mins) cleared the fault codes and they havent come back.

Hello Guys, I am facing this issue since last 6 months the car is shaking in idle and the exhaust is loud.
I went to the dealer and it turned out that the intake plate was cracked and i replaced it.
after that i had a check engine light and when i checked it showed P2190 and the dealer told that its from the MAF so i cleaned both of them and now i am having two coded P2190 and P2188 and the live data for self adaptation shows that both right and left is -6.
And the engine rattles when is start it when its warm and its little bit shaking in idle.

please help

Hey mate, I’ve been through this exact headache with my own M156. If you’re still getting P2188 and P2190 after replacing the intake plate and cleaning the MAFs, I’d suggest checking the fuel pump pressure control module — it’s in the boot, right side, near the battery. These modules can fail or send incorrect pressure to the rail, making the car run rich at idle and triggering those codes. It won’t always throw a direct fault for the module itself — just symptoms like rich mixture and rough idle.

Remove it, check it with a multimeter — resistance and continuity — and compare values across the pins. If it’s faulty, it won’t regulate pressure properly, even if the pump is fine. I replaced mine and it cleared both codes straight away. Let me know how you go.

Hi friend, I know this is old, but now I have the same two codes on my ml63. Do you know what caused it?

Hi, im also facing this issue eversince i installed a supercharger, keeps fluctuating when idling and in cold start it doesnt hold revs....I have also got codes related to fuel pump and fuel regulator, what's the fix to this?

Having the same codes and symptons, can somone give me a hand as to where exactly the Fuel Pump Control Module is, I have all 3 carpet trim panels out in the boot and cannot for the life of me find it. Prior guy above suggested it was in the boot near battery... pls help haha.

Hi bro,
Can you please post a photo of the part and where is located?

Thanks

Hi,
Can you please post pics of the part and the location? That will be very helpful
thanks