Please help DTC P0299
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Junior Member
Joined: Jan 2024
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2017 Mercedes Benz GLS550
Please help DTC P0299
Disclaimer:
Hi I’m still semi-new to the brand and forum. So I apologize if I am not up to date on the brand lingo and site functions. I am also on mobile.
Onward to my issue at hand; I have a 17 GLS550, yesterday afternoon check engine light came on, there is no difference in performance or the way it feels. No noticeable anything. I have a very basic scan, used it today to scan it, came up with code P0299 Turbocharger A under boost. From my basic understanding of turbos, I checked the air-filters they’re clean and not clogged. I checked the air inlet tube with the felt like section that likes to rip/tear. I recently replaced the driver side because of a rip in it. Today I noticed the passenger side had a tear in it. Could this be the issue? I don’t think it would be. My reasoning is under post would imply not enough air going in to turbo or it’s getting dumped at the waste gate. But I have been wrong before. Anywho just ordered a passenger side air intake hose because needs to be replaced anyway. But I am not familiar with this engine and/or turbo set up. Any help on trying to self diagnose this code would be greatly appreciated.
Hi I’m still semi-new to the brand and forum. So I apologize if I am not up to date on the brand lingo and site functions. I am also on mobile.
Onward to my issue at hand; I have a 17 GLS550, yesterday afternoon check engine light came on, there is no difference in performance or the way it feels. No noticeable anything. I have a very basic scan, used it today to scan it, came up with code P0299 Turbocharger A under boost. From my basic understanding of turbos, I checked the air-filters they’re clean and not clogged. I checked the air inlet tube with the felt like section that likes to rip/tear. I recently replaced the driver side because of a rip in it. Today I noticed the passenger side had a tear in it. Could this be the issue? I don’t think it would be. My reasoning is under post would imply not enough air going in to turbo or it’s getting dumped at the waste gate. But I have been wrong before. Anywho just ordered a passenger side air intake hose because needs to be replaced anyway. But I am not familiar with this engine and/or turbo set up. Any help on trying to self diagnose this code would be greatly appreciated.
Junior Member
Joined: Sep 2007
Posts: 32
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From: Conway, AR
2015 GL550
When I got that code I put in new air filters and cleaned out the air filter housings. Error then went away inside 20 miles of driving. I'm not saying this is the surefire fix but it worked for me. I put in the OEM paper filters. Thought about K&Ns or other 'high performance' filters but from what I read the OEMs are best for a turbo charged engine.
Thread Starter
Junior Member
Joined: Jan 2024
Posts: 19
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2017 Mercedes Benz GLS550
When I got that code I put in new air filters and cleaned out the air filter housings. Error then went away inside 20 miles of driving. I'm not saying this is the surefire fix but it worked for me. I put in the OEM paper filters. Thought about K&Ns or other 'high performance' filters but from what I read the OEMs are best for a turbo charged engine.
thank you! I will pick some new filters up and try that. I looked at mine and they seemed good but who knows? Definitely worth a try. Thanks again
Junior Member
Joined: Sep 2007
Posts: 32
Likes: 5
From: Conway, AR
2015 GL550
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Joined: Nov 2014
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2013 GL450
Thread Starter
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2017 Mercedes Benz GLS550
So here it goes…
Thanks for asking the question. So after my first update the car ran fine for about 2 weeks. Then the CEL came on again with the same code P0299. After more research and asking around I purchased a mityvac pump. I used this to pull vacuum on each waste gate valve actuator, I pulled enough vac on them to extend the rod all the way then held it for 15 minutes. Once I confirmed no leak on each side I was left scratching my head…but excited because that means turbos probably won’t be the issue. So after lots more research, mainly on here and YouTube to be honest. I came up on the pressure solenoid and little check valves in those lines. After inspecting the check valves for oil and finding them relatively clean I went on to the solenoid. I tried testing it but was not too confident in my execution of said test. But I don’t know, call it intuition, but I decided to replace the solenoid anyways, I found a seller on eBay with same part numbers for like $28. Thought to myself I’ll order it, if it works for 6 months then takes a crap on me I’ll at least know what I need to order. So here we are today, replaced pressure solenoid and still not codes. Hope this helps, I replaced both; engine air filters and pressure solenoid, the solenoid has been the actual fix in my case. I attached picture of exact items I purchased. For reference I have a 17” GLS550
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MBWorld Fanatic!
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From: Chicago
E63 SL55 996TT C5Z06
Hi @ItsMrG - I have the same situation. Do you have a DIY on how you placed replaced that solenoid? This code keeps coming back every two weeks. It clears itself when I drive very casually, but then when I get on the expressway, Infor to pass somebody it always comes back
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Thread Starter
Junior Member
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2017 Mercedes Benz GLS550
Sorry no DIY
Hi @ItsMrG - I have the same situation. Do you have a DIY on how you placed replaced that solenoid? This code keeps coming back every two weeks. It clears itself when I drive very casually, but then when I get on the expressway, Infor to pass somebody it always comes back
MBWorld Fanatic!
Joined: May 2010
Posts: 1,227
Likes: 185
From: Chicago
E63 SL55 996TT C5Z06
@ItsMrG hey that video is super helpful. Thanks so much! I’m probably just gonna buy the part for 40 bucks and replace it myself! Thanks again for taking the time to reply!
