Hello, I hope someone can help. The Check Engine Light warning has been going coming on and off on my Mercedes GL450 US model. Then, the CEL warning become permanent. I used Star C3 diagnostic tool to test the issue. The diagnosis is saying different things after deleting the faulty codes few times:
1. B2/5 (Hot film mass air flow sensor): Open circuit / Short circuit to ground or to positive (P0102).
2. B2/5 (Hot film mass air flow sensor): Loose contact with low frequency (P0104)

The the driving experience is always great. I cannot feel any issues with the acceleration or engine behavior. I believe it is working perfectly.
I replaced the Mas Air Flow sensor with new OEM Bosch sensor. The problem is still persists. The CEL is still in place. I totally lost and not sure what else can be done to get rid of this issue. Any ideas are highly appreciated. Thank you in advance.

 

It's a bit hard to guess which vehicle/engine you are talking about since no specific GL year / model appears in your profile or this post.
Is it diesel or gas? Are you in the USA, europe, or?
Is there more than one MAF sensor, and if only one, is the wiring intact? Is there a dealer available to you that you can get to assist in diagnosing the issue?
Hard to guess on any of these things since only you know.

 

I agree. I corrected my initial post. This car has only one MAF sensor. The car is USA model. No dealer is available. Thank you again.

 

Two things come to mind. One is bad connector/ harness from Maf to ecu. Test fOr continuity and shorts. Second thing is your intake manifold is not inserted properly or you have a hose unplugged/ cracked/ etc and you are getting unmetered air.

What is the freeze data when the codes are thrown? This will tell you what went out of whack and will provide further clues.

Lastly, just humor me- reset all adaptations in the bosch engine mgmt module (via das).

 

I finally was able to nail down the issue. The harness connector is badly designed. It was very difficult to disconnect it from MAF sensor and the pin from sensor was damaged. As a result, the connection was not tight. I had to fix it using tight wire. Now, it works perfectly. I just surprised how badly harness connector is designed.