maralorenz5
Mercedes GLK diesel check engine light and power loss resolved
Summary of the thread
A 2008 Mercedes GLK diesel experienced a check engine light, power loss, poor engine response, and increased fuel consumption, with a diagnostic scanner indicating a boost pressure control fault. Possible causes included a faulty vacuum switching valve, a vacuum leak, or a defective pressure sensor. After consulting a workshop, the issue was identified as a defect in the vacuum switching valve, which was replaced, resolving the problem.
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4 comment(s)
maralorenz5 (community.author)
Bypass valve, huh? Where exactly is that located, and how would I check it? Also, could a faulty pressure sensor cause these issues too? I'm not really sure where to start looking for a vacuum leak.
milasilver10
The valve is near the turbo, but honestly, chasing vacuum leaks without proper tools is a pain. If you're seeing a boost pressure fault consistently, and experiencing all those symptoms, I'd suggest getting it checked by a workshop. They can diagnose the vacuum system properly.
maralorenz5 (community.author)
Took your advice and brought it to the workshop. It was a defect in a vacuum switching valve, just like the internet suggested. They replaced it, and now the GLK is back to its old self. Total cost was 140€, which isn't too bad. Appreciate the help!
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MERCEDES
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GLK
milasilver10
I had similar symptoms on my GLK. Check the bypass valve and associated vacuum lines. A pressure drop there will definitely cause turbo lag and reduced power.