P0299 on Ford TDCi – Turbo Underboost

Platform‑specific notes for diagnosing underboost on Ford TDCi and EcoBlue diesel engines.

Typical Symptoms on Ford Diesels

  • Sluggish performance, especially on hills or when loaded.
  • Excessive smoke under load if boost is very low or fuelling is incorrect.
  • Sometimes combined with DPF or EGR‑related codes.

Common TDCi‑Specific Causes

  • Split boost hoses or loose clamps between turbo, intercooler and inlet manifold.
  • Sticking variable‑geometry vanes due to soot build‑up.
  • Vacuum leaks or faulty boost control solenoids on vacuum‑controlled systems.
  • Exhaust leaks before the turbo affecting its ability to make boost.
  • DPF that is heavily loaded, causing the ECU to limit torque and boost.

Suggested Test Plan

  1. Log commanded vs. actual boost pressure under a controlled full‑throttle pull.
  2. Visually inspect all boost hoses, intercooler joints and clamps.
  3. Check vacuum supply, vacuum hoses and boost control solenoid operation.
  4. Evaluate DPF load values and regeneration history.
  5. Where possible, check turbo actuator movement directly and compare with specs.