michaelmoon73

Mercedes Viano diesel fault code and reduced power

My 2011 Mercedes Viano diesel is throwing a fault code and has noticeably reduced engine power. Mileage is sitting at 265749 km. I've run a vehicle diagnostics check with my auto scanner and it's pointing towards an engine issue. Dashboard light is on, naturally. Suspecting dodgy chip tuning from a previous owner. Anyone else experienced similar?

4 comment(s)

Sounds familiar. Had a similar issue with my Vito, same symptoms – reduced power, fault code. First thought it was the turbo, but then I started suspecting some third party tuning. Any idea what the exact fault code is? Might help narrow it down.

The auto scanner flagged P0299, underboost. But the thing is, the turbo seems fine. No unusual noises, no excessive play. Could the chip tuning really cause a fault code like that even if the turbo itself is working correctly?

Yep, P0299 was the exact code I got! And yes, aftermarket chip tuning can absolutely mess with the ECU and throw that code even if the turbo is mechanically sound. The tuning probably pushed the turbo beyond its safe operating limits. I'd recommend getting it checked at a proper workshop.

Thanks for the info. Took it to a workshop as suggested, and you were spot on. They confirmed the chip tuning was causing the issue. They reflashed the ECU, reverting it to the stock settings. Cost me 180€, but the engine power is back, and the fault code is gone. Appreciate the help!

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