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VNT-Turbo adjustment defective

Volvo S40 (2004-), V50, V70 (2008-), S80 (2007-), C30, C70 (2006-), XC60 (-2017)

17.02.2026

Here we show an example of a common fault pattern in electronically controlled turbochargers with variable nozzle turbocharger (VNT). With these turbochargers, boost pressure control via solenoid valves and pressure cans is completely eliminated.


Electronically controlled VNT turbochargers have a geared motor for adjusting the turbine geometry. This component is subject to very high thermal loads and constantly adjusts the turbocharger geometry in fractions of a second. It also feeds its position back to the engine control unit. 

If it is defective, the intake system may be damaged because the charge air pipes or intercooler may not be able to withstand the excessive pressure.

A typical damage to the VNT adjustment is the worn pinion of the adjustment lever, clearly visible in the picture. In such a case, the engine control unit will definitely set an error and possibly go into emergency mode. 

If the turbine geometry is now in the wrong position, the turbocharger pressure is not regulated during shifting or idling and overpressure can occur. 
If the turbocharger is otherwise intact, the actuator can be replaced individually if available.The vehicle manufacturer has not provided for such a part replacement.
  • All notes serve only as an example and do not replace the workshop instructions of the automobile manufacturers! All information is supplied without guarantee!

Additional information...

  • 1090715 1090715: Boost pressure control Electronics unit Electric-mechanical
  • 1038326 1038326: Turbocharger VNT-Turbo