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I recently bought a MB C300 with the check engine light on for P0106 MAP sensor with O2 sensor codes which I assumed were from the computer trying to compensate for having no manifold pressure value. I looked and the MAP sensor was broken, and the hose was plugged so I replaced both and cleared codes, but they came back. Later I found another vacuum leak and replaced that hose and cleared codes, but the light came back on after driving awhile and testing by raising the rpms. I don't know if this would mean anything but when AutoZone scanned the first time, the MAP sensor code was primary and the O2 sensor codes were secondary but the second time they read codes it was the other way around. Not sure if I should be chasing down more vacuum leaks, cleaning the egr, checking O2 sensors, or something else.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Sounds like fun. Did you get the car for cheap? Is this your first Mercedes? Have you performed a "smoke test" on the engine and vacuum lines?
Diagnosing a mercedes can be tough since the failure of one component can trigger codes for others, while there really is nothing wrong with them. I've never come across "primary" or "secondary" DTCs determined by a scan tool, not even XENTRY. How did the AutoZone guy determine which was which?
You really need to include some missing information in your profile, like your location (what country) and the year of your car.
Sounds like fun. Did you get the car for cheap? Is this your first Mercedes? Have you performed a "smoke test" on the engine and vacuum lines?
Diagnosing a mercedes can be tough since the failure of one component can trigger codes for others, while there really is nothing wrong with them. I've never come across "primary" or "secondary" DTCs determined by a scan tool, not even XENTRY. How did the AutoZone guy determine which was which?
You really need to include some missing information in your profile, like your location (what country) and the year of your car.
It is my first Mercedes and I got it for cheap. It's a 2011 C300 with the M272 engine and 4Matic. I haven't had a smoke test yet since I just got it, but I am looking into getting one soon. For now, I am going to try to replace as many of the bad vacuum lines as I can and take off the intake to inspect it and replace the gaskets.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Do you know your full model designation? If not, run your VIN at www.lastvin.com and at the top of the page the designation appears as 204XXX (see below). That will help me identify the procedures for removing the intake manifold. And, since this is your first Mercedes, be sure to get an adequate scan tool.
A scanner is absolutely the first "accessory" you want to get. Otherwise, you'll never really know what problems lurk unless you take it to a shop and you'll pay more to have the shop scan the car for you. Check Amazon for:
iCarsoft MB V3.0 (not MB II)
Launch Creader Elite Benz
Foxwell NT510 Elite
BlueDriver
BlueDriver is the least expensive and a pretty good scanner if you just want to know what codes are there and to clear them. Beyond that, you'll want one of the others. They all will automatically identify your car and scan for codes, and give you the option to clear them. The top 3 will allow you to do other things if you ever start tinkering, such as changing your brake pads, resetting maintenance counter, etc. Even if you don't do your own maintenance, it's good to know what is going on. You have a complex vehicle and need to know when something important is wrong or not.
The other thing you want is to get a copy of the electronic shop manual (called the WIS) and the EPC (electronic parts catalog). There are copies on eBay for about $20-$30. They all run in a virtual machine since configuring them can be complicated. The VM versions have the software configured to run in something like VBOX. This is just an EXAMPLE. Look around and compare vendor ratings, etc.
Thank you so much for all of this valuable information! I'll be sure to get a scanner and a manual since they are definitely very helpful. I usually do all of my own maintenance and repairs so I'm sure it will be a good investment.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by MB_C300.
Thank you so much for all of this valuable information! I'll be sure to get a scanner and a manual since they are definitely very helpful. I usually do all of my own maintenance and repairs so I'm sure it will be a good investment.
You're welcome.
These are great cars when properly maintained and running right. But they can be expensive if you don't do your own maintenance. And to do that, you need the right tools. I have found that they are actually easier to maintain than other european car brands like VW and Audi.
Lastly, there is the official mercedes diagnostic tool called XENTRY/DAS (sometimes also referred to as STAR Diagnostic). I don't know your budget, but if you stay with Mercedes you will eventually want to get one. There are Chinese clones available on eBay, AliExpress, and various companies that sell OBD stuff. You'll need to do your research because not all are good quality. XENTRY/DAS or STAR Diagnostics comprise a laptop or tablet running Windows, a multiplexor (there are C3-C6, but you want a C4), and the software. Again, you'll need to do your research on this. I've been lucky with the clones I've gotten, but it's been several years now. If you search this forum, www.benzworld.org, and YouTube, you'll learn a lot. There is also a member and sponsor here called @BenzNinja that you will want to keep in mind that sells a diagnostic and programming service if you run into electronic problems with your car, which can happen.
Good luck.
Last edited by JettaRed; Nov 30, 2023 at 03:06 AM.
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