Fuel and air

P0299 — Turbocharger/Supercharger Underboost Condition

Severity: medium Drive with care, to a shop

What P0299 means

The engine control unit compares actual boost pressure, read by the intake pressure sensor, with the target for the current load. When actual boost stays below target, it stores P0299. This usually points to a charge-air leak, a boost control problem, or a worn turbocharger or supercharger.

Symptoms

  • Check engine light on
  • Sluggish acceleration and loss of power
  • Limp mode
  • Higher fuel consumption
  • Whistling, hissing, or chuffing from the engine bay under throttle
  • Black or gray exhaust smoke

Possible causes

  1. Charge-air leak: cracked or loose hose, bad clamp, or a leaking intercooler or intake pipe
  2. Wastegate stuck open or a faulty actuator
  3. Faulty boost control solenoid or cracked vacuum lines
  4. Faulty boost pressure or MAP sensor
  5. Worn turbocharger: shaft play or damaged turbine or compressor wheels
  6. Clogged air filter or intercooler, or an exhaust restriction such as a plugged catalytic converter or particulate filter
  7. Damaged wiring or connectors to the sensor or solenoid

How to diagnose

  1. Read all codes and freeze frame data and note any related air or fuel codes
  2. Inspect the air filter, charge-air hoses, clamps, and intercooler for cracks, oil residue, or loose connections
  3. Compare commanded and actual boost in live data during acceleration
  4. Pressure-test the charge-air system at low pressure to find leaks
  5. Check wastegate or variable-geometry actuator movement and boost control solenoid operation
  6. Inspect vacuum lines, connectors, and the wiring and ground to the boost sensor
  7. Check turbo shaft play, wheel condition, and oil in the intercooler
  8. Check the exhaust for restrictions and measure backpressure if needed

Common fixes

  • Replace damaged hoses and clamps and eliminate leaks
  • Replace the boost control solenoid, vacuum lines, or wastegate actuator
  • Replace the boost pressure or MAP sensor
  • Clean or replace the intercooler and replace a clogged air filter
  • Repair or replace the turbocharger and fix the root cause, such as lubrication problems
  • Repair wiring and connectors

P0299 on different brands

Ford · manuals
On Ford, P0299:00 is documented as Turbocharger/Supercharger A Underboost Condition in its gasoline-engine OBD monitoring; it identifies the detected condition rather than a confirmed failed part.

Questions and answers

What does code P0299 mean?

The boost pressure measured by the sensor is lower than what the ECU is requesting. The most common causes are a leak in the charge-air hoses, a wastegate or boost solenoid fault, and less often a worn turbo.

Can I drive with a P0299 code?

Briefly and gently, yes, but expect reduced power and possible limp mode. Don't put off diagnosis, especially if you hear a turbo whine or see smoke.

How can I find the cause of P0299 myself?

Start by checking hoses, clamps, and the intercooler for cracks and oil traces, then inspect the boost solenoid's vacuum lines. If everything looks fine, you'll need live data and a pressure test.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.