Experiencing a sudden loss of power in your Mercedes Benz, especially when accelerating or going uphill? You might have encountered the dreaded limp home mode, accompanied by the engine management light illuminating your dashboard. For Mercedes Benz owners, particularly those with models like the Sprinter van, this issue can often be linked to the P0299 error code: Turbo Underboost.
Initially, I faced this exact problem with my van. Short trips around town seemed normal, but as soon as I exceeded 40 mph or attempted a longer drive, the engine performance would drastically drop. It felt like the turbocharger simply wasn’t engaging, leaving me with significantly reduced power. This “limp mode” restricted the engine’s RPM, making driving at higher speeds or on inclines a real struggle.
My first step was to use a basic OBD2 scanner, which quickly revealed the P0299 code. This code indicates a turbo underboost condition, suggesting that the turbocharger isn’t producing the expected level of boost pressure. The potential causes for this issue are numerous, ranging from simple fixes to more complex problems. Common culprits include leaks in the intercooler piping, faulty vacuum lines, or, in more severe cases, a failing turbocharger itself or issues with the intake system, specifically a known problem with cracked intake pipes in the OM651 engine.
I began troubleshooting by visually inspecting all accessible pipes and hoses connected to the turbo and intercooler system. I checked for any obvious splits, cracks, or loose connections. One prominent red pipe, running from the intercooler to the turbo, seemed like a potential point of failure, but upon closer examination, it appeared intact. I even replaced the gaskets at both ends of this pipe as a precautionary measure, but unfortunately, this didn’t resolve the problem.
Seeking further assistance, I took my van to my regular mechanic. He conducted a similar inspection, covering areas I couldn’t easily reach, and consulted with other mechanics. The consensus leaned towards a faulty turbocharger. Given the significant cost of a replacement turbo, around £550 for a reconditioned unit, I was hesitant to jump to this conclusion without further investigation. I decided to seek out a specialist with expertise in Mercedes Sprinter vans.
A quick online search for a “Sprinter specialist Croydon” led me to MerxWerx, a mobile Sprinter repair service. I contacted Peter at MerxWerx, and he agreed to come to my location the next day. Peter’s expertise was immediately apparent. After a brief assessment, he confidently stated that the turbo itself was likely not the issue, mentioning that turbos on these vans “rarely go wrong.” Instead, he suspected a vacuum leak, specifically somewhere in the vacuum system before the turbo, on the same side of the engine as the EGR valve and cooler.
While Peter was confident in his diagnosis, he needed a vacuum testing kit to pinpoint the exact faulty component. He suspected one of four identical vacuum transducers in that area. He returned the following Monday with the necessary testing equipment. Using the vacuum tester, Peter quickly confirmed his initial diagnosis: the problem was indeed a faulty turbo transducer.
Faulty turbo transducer responsible for P0299 error code in Mercedes Benz Sprinter, part number A 009 153 31 28.
Because of his experience and accurate preliminary diagnosis, Peter had come prepared with a new turbo transducer. He replaced the faulty unit, and just like that, the issue was resolved! Since then, I’ve driven the van extensively, and the limp mode and P0299 error have not returned. The van now runs smoothly and with full power.
The part number for the turbo transducer is A 009 153 31 28. If you are in London or the surrounding areas and are experiencing puzzling issues with your Sprinter, I highly recommend contacting Peter at MerxWerx (http://www.MerxWerx.com). His expertise and mobile service were invaluable in resolving my P0299 turbo underboost issue quickly and efficiently, saving me from potentially unnecessary and costly turbocharger replacement.
In conclusion, the P0299 code on your Mercedes Benz doesn’t automatically mean a turbo replacement is necessary. Vacuum leaks, particularly a faulty turbo transducer, can be a common cause of turbo underboost. Seeking expert diagnosis, like from a Mercedes Sprinter specialist, can save you time, money, and ensure the correct repair is performed, getting you back on the road with optimal engine performance.
