P0299: Turbocharger/Supercharger "A" Underboost Condition

P0299 means the turbocharger is not producing enough boost pressure to meet the ECU's target value during normal driving. The engine will feel noticeably less powerful, especially under acceleration. Common causes include boost leaks in the charge piping, a stuck-open wastegate, or a worn turbocharger with failing bearings.

P0299 is a fuel system-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0299 and illuminates the check engine light.

If your vehicle has triggered P0299, you may notice one or more of these symptoms:

• Check engine light on
• Significant loss of power and acceleration
• Limp mode (reduced engine power warning)
• Turbo whistle absent or reduced
• Black smoke from exhaust under acceleration
• Higher than normal exhaust gas temperatures

Here are the most common causes of P0299, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. You can drive to a workshop but expect significantly reduced power. The engine is not in immediate danger but the underlying cause should be repaired soon to prevent further turbo damage.

Follow these steps to pinpoint the root cause of P0299:

1. Use a scan tool to monitor actual boost pressure versus target boost. If actual pressure is consistently 0.3+ bar below target under load, the underboost is confirmed
2. Check the air filter first. A severely clogged filter restricts airflow and limits boost. Replace if dirty
3. Perform a boost leak test by pressurising the intake system with compressed air (0.5-1 bar) and listening/feeling for leaks at intercooler pipes, hose connections, and the intercooler itself
4. Inspect the wastegate by checking if the actuator rod moves freely. Disconnect the vacuum/pressure line and verify the wastegate closes fully. A stuck-open wastegate allows exhaust to bypass the turbo
5. Check the turbo for shaft play by removing the intake pipe and wiggling the compressor wheel. More than 1 mm of radial play indicates worn bearings
6. If no boost leaks or turbo wear found, check for exhaust restrictions (blocked DPF or catalytic converter) using a backpressure test

Repair costs for P0299 vary depending on the root cause and your vehicle. Here are typical estimates:

P0299 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0299 or indicate related issues: