P0299 on BMW Diesel – Turbo Underboost

BMW diesel-specific notes for P0299. Often caused by charge-air leaks, actuator control issues or soot-related turbo vane sticking.

Common Causes

  • Split boost hoses or loose clamps.
  • Vacuum leaks / control solenoid faults on vacuum-actuated turbos.
  • Sticking variable-geometry turbo vanes from soot.
  • DPF overload limiting torque and boost request.

Suggested Test Plan

  1. Compare commanded vs actual boost under load.
  2. Pressure test boost system and inspect intercooler joints.
  3. Check actuator movement and vacuum supply where fitted.
  4. Assess DPF load; fix soot-producing faults early.