Diagnostic Overview
Volvo fault code P0046 is a turbocharger or VGT control-performance fault. The ECM is seeing that the turbo control circuit or actuator response does not match what was commanded. On VGT-equipped Volvo engines, this may involve the turbo actuator, vane movement, wiring, or boost-control feedback.
Likely Causes
Failed VGT actuator; sticking turbo vanes; actuator calibration issue; wiring or connector problem; poor power or ground; soot buildup; boost or exhaust leak.
What To Check First
Check commanded versus actual turbo position, inspect actuator wiring, perform actuator calibration/test, verify vane movement, and pressure-test the intake system.