vincent_blade3
SM3 P0299 Underboost
Summary of the thread
The conversation revolves around a 2014 Renault SM3 experiencing a P0299 underboost code, leading to reduced power, poor engine response, and increased fuel consumption. The issue is suspected to be caused by a faulty electrical bypass valve on the turbo wastegate. A similar experience shared by another individual confirmed that a defective turbo actuator was the problem, and replacing it resolved the issue, restoring the car's performance.
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4 comment(s)
vincent_blade3 (community.author)
Yeah, spot on! Loud hissing, especially when the turbo is trying to spool up. Did yours also throw that underboost code, P0299? Any other codes or weird behavior before you figured it out? I'm guessing it's the actuator valve, but wanted to see if you had the same experience.
noahsteel1
Yep, P0299 was the culprit for me too. Honestly, after chasing vacuum lines and sensors, I just gave up and took it to a workshop. They diagnosed a defective turbo actuator in like, five minutes. Saved me a ton of headaches. I'd suggest you do the same.
vincent_blade3 (community.author)
Thanks! Confirmed my suspicions and the diagnosis. Took it to a mechanic and they swapped out the turbo actuator. Cost me 250€, but the car is running like new again. That electrical bypass valve can really cause some havoc! Appreciate the help!
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RENAULT
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SM3
noahsteel1
Whoa, those are rough symptoms! I had something similar on my SM3. Was it like a really loud, obvious hissing under acceleration? Almost like a boost leak, but more electrical?