2011 GLK350 CEL P171 P174
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2011 GLK350
2011 GLK350 CEL P171 P174
Hello anyone out there have any experience or advice on a P171 and P174 codes? My light turned on a bit ago and it was intermittent at first then went solid. I cleaned the MAF and replaced one of the MAF gaskets. Checked my air filter compartment to be seated correctly. Smoked intake. Took to dealer they found intake manifold not responding so I authorized them to replace. They then recommended replacing the downstream O2's which I decided to do myself. With all that done I still have CEL light on. I have scan tools but not experienced at reading fuel trims and o2 voltages so looking for some advice on what I need to be looking for to finish diagnosing this issue. My current thoughts could be faulty MAF, Fuel pump issues, exhaust leak, bad upstream cat??? Thanks in advance for any help.
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From: Northern NJ
GLK 350 / Porsche 993
Mileage?
Maybe PCV system per below video?
Bad cat would give you different downstream o2 codes
Besides fuel pump it could be injectors - but I doubt it. I think you'd have other issues/codes if it was fueling issue.
Bad MAF is a potential, but my bet is on something plastic cracking and creating vacuum leak.
I have 2010 with 119k miles.
Maybe PCV system per below video?
Bad cat would give you different downstream o2 codes
Besides fuel pump it could be injectors - but I doubt it. I think you'd have other issues/codes if it was fueling issue.
Bad MAF is a potential, but my bet is on something plastic cracking and creating vacuum leak.
I have 2010 with 119k miles.
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Newbie
Joined: Nov 2022
Posts: 2
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2011 GLK350
The mileage is just over 120K, I decided to swap MAF and there is two special orange gaskets on the elbow after the MAF that I replaced. That seemed to be my problem. My fuel trims returned normal and car driving normal again. Thanks for some suggestions!
