Turbo Underboost

Doug McAninch

New member
Sep 14, 2020
I drove my recently purchased used 2007 Jayco Seneca motorhome with a Duramax 6.6l over the weekend. The motorhome was serviced in December and due to Covid and trying to sell the vehicle, we do not think the previous owner drove the vehicle much this year. After using the engine break on several hills, the vehicle started to blow black smoke. There was no loss of power, but then the engine light came on. We continued on as there did not appear to be any issues under the hood, no noise, and no loss of power. After several miles, the vehicle stopped blowing black smoke. When we got to a location to run the diagnostic, the error code was 'turbo underboost'. When we restarted the vehicle, the engine light was off. The vehicle appears to be operating normally. Comments?


Why do I keep doing this?
Staff member
Apr 19, 2008
Mid Michigan
Which engine model does it have? Considering its a 2007, Id assume LBZ....but you never know with motorhomes. Have to know the actual codes to even begin to guess though. Could be stuck vanes or vane position sensor, too?
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