P0299 — Turbocharger/Supercharger "A" Underboost Condition
Boost pressure under load is below the commanded value. Very common on turbodiesel and direct-injection turbo gasoline engines as the turbo system ages — typically a leaking boost pipe, a sticky variable-geometry vane assembly, or a wastegate that no longer holds.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Turbocharger
- Intercooler
- Intercooler pipe
- Wastegate actuator
- Vgt actuator
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Leak in intercooler pipe or hose
- VGT vanes stuck (diesel, soot buildup)
- Wastegate stuck open or weak spring
- Turbo bearing worn (preceded by oil consumption / smoke)
Possible symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
- Reduced-power or limp mode may occur
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.