2016 Mazda 6 2.0L Petrol · WJ66 DBZ

Soot accumulates in the intake manifold and EGR system, causing flat performance, poor economy and repeated regeneration trouble.

On 2.2-litre Skyactiv-D (SH-VPTS) diesel engines, the sequential twin-turbocharger assembly suffers from mechanical failure of the exhaust gas regulation valve (wastegate flapper) inside the turbine housing. The pivot pin and rivet holding the flapper fatigue and shear off, causing sudden loss of boost pressure at lower RPMs and triggering fault code P0299 (turbocharger underboost) alongside severe limp mode. In addition, turbocharger bearings are vulnerable to oil starvation caused by carbonised oil and soot accumulation from DPF regeneration cycles. Replacing the twin-turbo unit requires a revised assembly, new oil feed pipes and thorough oil flush.

The 2.2 Skyactiv-D engine is prone to premature erosion of the copper combustion chamber sealing washers beneath the fuel injectors. When a washer fails, high-pressure combustion gas blows past the injector into the rocker cover, rapidly baking the engine oil into hard carbon crust and granular sludge. This carbon debris migrates down into the oil sump and chokes the fine wire-mesh oil pump pickup strainer. Oil starvation follows, triggering low oil pressure warnings, grinding exhaust camshaft lobes, vacuum pump failure (causing stiff brake pedals) and catastrophic engine seizure. Preventative replacement of injector washers and sump strainer cleaning is essential.