TSB 14-0151POWERTRAIN DRONING NOISE - ACTIVE NOISE CANCELLATION (ANC) Publication Date: August 18, 2014 FORD: 2013-2014 C-MAX ISSUE: Some 2013-2014 C-MAX Hybrid and C-MAX Energi vehicles may exhibit a loud, low frequency, droning powertrain type noise when the engine is running. The noise c...