P0299 on Porsche: How to Diagnose & Fix
Turbo/Supercharger Underboost Condition
1 Porsche model · 1 documented issue · 1 critical · $2,500-$6,000 repair
P0299 on Porsche by model: symptoms, diagnosis and fix
On the base 2.0L 718 the single turbocharger and its electronic wastegate actuator are mounted low under the belly pan, exposing the actuator to road water, salt, and debris. Over time the actuator rod corrodes and seizes, so boost builds momentarily (e.g., ~15 psi) then collapses, or never exceeds ~5 psi. The result is sudden loss of power, juddery delivery under hard acceleration, and sometimes a PSM/engine warning; restarting the engine often temporarily restores boost. The 2.5L is less affected because its turbo sits higher in the engine bay. Porsche's official remedy for a failed actuator is replacement of the complete turbocharger; later parts have improved weather protection. This is distinct from the audible idle wastegate rattle in that it produces actual boost loss and turbo replacement.
Common Symptoms
- Sudden loss of boost / power
- Boost builds then drops to a few psi
- Juddery power under hard acceleration
- Engine/PSM warning light
- Power restored after engine restart
How to Fix
Diagnose with boost-pressure logging; freeing/greasing the actuator arm can be a temporary measure, but Porsche's fix is to replace the turbocharger assembly (under warranty/extended warranty where applicable). Use the updated turbo with improved actuator protection and inspect/seal the underbody exposure point.
Sources for this issue (3)
P0299 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0299 mean on a Porsche?
P0299 stands for "Turbo/Supercharger Underboost Condition." P0299 means the engine computer detected an underboost condition — the turbocharger or supercharger is producing less boost pressure than the PCM expects for the given conditions. The computer compares the manifold/boost pressure sensor reading to a target based on engine load, and when actual boost falls short, it sets this code. The most common real-world cause is a leak somewhere in the intake/charge-air path. You'll typically feel reduced power or sluggish acceleration, and the engine may go into a reduced-power mode. On Porsche it is documented across 1 model: 718 Cayman.
What are the most common causes of P0299?
The most common causes of P0299 are: Boost/intake leak (cracked or loose charge-air hose or intercooler), Faulty or sticking turbo wastegate or actuator, Stuck or clogged variable-geometry turbo vanes (VGT), Faulty boost pressure or MAP sensor, Leaking or disconnected vacuum/boost control lines, Restricted air intake or clogged air filter, Failed boost control solenoid, Worn or failing turbocharger. The specific cause varies by vehicle.
How much does it cost to fix P0299 on a Porsche?
Published repair estimates on Porsche range from $2,500 to $6,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0299 on a different make?
View P0299 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.