Approximately once a month I the CEL illuminates on my 2005 C230. The code is usually P201D-000. My iCarsoft scanner states, "This code is not found in the database." I found this old thread suggesting that cleaning the MAF solves the problem

I also had a one-time P2035 code which occurred on a 100-mile trip. The P201d code was the first one to set. My iCarsoft scanner also doesn't have the P2035 code in the database. I couldn't find anything M271-related on P2035. The information I have found suggest that the code indicates a malfunction in the Turbocharger/Supercharger Boost Sensor 'A' Circuit. This sensor is responsible for monitoring the boost pressure produced by the turbocharger or supercharger in a vehicle with forced induction. My thought is that the MAF problem may have had a cascade effect on the supercharger sensor.

Cleaning the MAF will require me to remove several parts - .

Before I undertake this task, I have few questions:

1. Has anyone else resolved this code by cleaning the MAF?
2. Although cleaning the MAF is less expensive than replacing it, this is not a job I want to complete twice. Should I plan to replace the MAF? The car has almost 200k miles on it.
3. Are there any other tasks I should complete while I have the air box removed?
4. Will cleaning or replacing the MAF resolve the P2035 issue?

Thanks in advance for suggestions and guidance.

The MAF is quite easy to get to. Basically you're rolling the dice on whether or not it can be cleaned and "fixed". If you really don't want to do the job twice, replace the sensor.

If you are fast, the job will take 1-2h. It's attached to the airbox.

Thanks for the reply Slammer.

I posted a similar question on Benzworld and the moderator pointed me to the list of DTC's on Benzbits. (I have attached a copy of the pdf.) When I scrolled down to page 3 of the document, it showed "201D - [1] Catalytic converter Effect is insufficient. [P0420]."

I'm planning to complete some more research before I start taking things apart. I'm confident that I would be able to clean or replace the MAF if that is the problem. However, the list of fault codes on Benzbits is pointing in the direction of an aging catalytic converter.

The person who posted the thread I linked only had 7 posts and hasn't been on the forum since 2016. It's possible that cleaning the MAF and clearing the code made it appear that the problem was resolved. I can't put as much faith in his post as I do in the posts from long-term owners/forum members.

Given the codes you've encountered, it’s crucial to dig deeper. For the P201D code, it's surprising that there's limited information available. However, its appearance alongside P2035 could mean there's an underlying issue with the air intake system. Often, these errors can originate from something as straightforward as a loose or compromised vacuum line affecting both the MAF and the supercharger systems. Also, check the condition and connection of the Boost Sensor ‘A' Circuit, which might be affected by sensor faults or wiring issues. Less common culprits like an intermittent electrical fault in the harness leading to the MAF or the boost sensor could also play a role, potentially causing sporadic misreads that trigger these codes.

I agree. I have found that clearly identifying the problem is crucial before jumping in and starting to replace parts. For example, a few years ago the CEL would illuminate every time I filled the car with gas. I forget what the code was, but it is possible that it was also P201D. I didn't pursue repairing it at the time. Then, my radiator started to leak which required that I disassemble the supercharger pipes to replace it. In the process of reassembling the supercharger pipes, I noticed that the O-rings in the joints were not fitting well. I replaced all of the O-rings. That seemed to also cure the CEL issue which didn't reappear for about two years.

About 3 months ago, my car suddenly lost power and the CEL illuminated. It felt like the supercharger wasn't working. Loss of power thread. That turned out to be a damaged hose in the supercharger system. The damaged hose was obvious once I started to look in the right place.

I am planning to take a few hours to study the car and see whether I can find another obvious problem like a damaged hose or wire. The light has triggered three times. The first incident occurred on a twenty-mile trip which contained some sustained driving at 65-70 mph. The two recent incidents occurred when I was on 100-mile trips and the car was operating at about 70 mph and slightly less than 3000 rpms. I don't know whether the driving conditions are a clue to the source of the problem, but it seems odd that the CEL does not appear to be triggered during low-speed/stop-and-go driving.

Thanks for the reply.