Hi forum members, I am new to the forum and to Mercedes so I will be needed some solid mechanical advice. I don’t actually own a Mercedes, I am here on behalf of my son in-law who owns a 2011 C300. He has been driving with a CEL for some time and he finally asked me for advice on his car. I’m fairly knowledgeable when it comes to working on cars, but know little about the Mercedes brand. I know that one code can trigger another and on down the line, so I’ll list them all and see where everyone thinks we should go first. P0410 (air system), P2414 (02 sensor exhaust error), P2626 (02 sensor pumping current trim), last but not least P2196 (sensor signal biased/stuck). I know he should be running premium gas, but just uses 87 octane. Should we just try some heavy duty fuel system cleaner to see if that will do anything first, or is there a more serious problem? Any help would be appreciated.

 

Hello and welcome to the forum! How does the car run? Rough? What happened that made you want to pull the codes?

 

Not sure what finally pushed him over the edge. Maybe he is thinking about passing echeck on his next license renewal. I think it started smelling foul when running and he questioned me on what caused it. He also stated that there was some kind of loud howling noise on the right side of the engine, towards the firewall. It did go away, but thinks that it was right after that the CEL came on.

 

As you suggested, I would do an entire system flush and take care of the o2 sensor codes - they're likely related to the same issue which caused the CEL. You should also tell him to start using a higher octane gas or at least start using fuel additives often. The engine is tuned to a certain octane and going below for long periods of time can and will harm the engine. Let us know if you have any other questions or if we can assist with any future part needs. Thanks.