Turbo/Supercharger Underboost Condition
The P0299 code means the vehicle's onboard diagnostic system has detected: Turbo/Supercharger Underboost Condition. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $2,500 (parts and labor)
Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Common Symptoms
- Check Engine Light on
- Significant loss of power during acceleration
- Turbo does not build boost pressure
- Whistling or hissing noise from engine bay
Not sure this code matches what your car is doing? Try the guided checker: White, blue, or black smoke →
Probable Causes (Ranked by Likelihood)
- Boost leak in intercooler hoses or pipes Very High
- Stuck or seized turbo wastegate High
- Failing turbocharger (worn bearings or shaft) Moderate
- Clogged catalytic converter restricting exhaust flow Low
Step-by-Step Diagnostic Procedure
-
Perform a boost leak test: pressurize the intake system to 15 psi and listen for leaks. Check all intercooler pipes, hose clamps, and the intercooler itself.
-
Inspect the wastegate actuator. Manually operate it to check for binding or seizure. Apply vacuum to check the diaphragm.
-
Check the turbocharger for shaft play by hand. Some side-to-side (radial) wiggle is normal in journal-bearing turbos and is not by itself a failure. What matters: spin the wheel and rock the shaft -- the compressor and turbine wheels must NOT touch the housing, and in-and-out (axial) end play should be very small. Condemn the turbo for wheel-to-housing contact or excessive axial play, not for radial wiggle alone; check the turbo's service spec for exact limits.
-
Measure exhaust back pressure before the turbo. High back pressure from a clogged catalytic converter can prevent the turbo from building boost.
Common Fixes by Vehicle
What techs usually find when diagnosing P0299 on specific vehicles — tap your vehicle for the fix and the exact part:
2011-2020 Ford F-150/Explorer/Edge 3.5L/2.7L EcoBoost moderate DIY
Turbo underboost on EcoBoost engines is most commonly caused by a leaking charge air cooler (intercooler). Ford issued TSB 14-0131 for charge air cooler condensation and leaks on 3.5L EcoBoost. Check all boost hoses and clamps first -- a loose clamp on the intercooler pipe is the cheapest fix. If hoses are tight, pressure test the charge air system to 20 PSI and listen for leaks. A cracked intercooler tank needs replacement.
Labor: 1-3 hours2009-2019 VW GTI/Jetta/Passat/Audi A4 2.0T TSI/TFSI easy DIY
The VW/Audi 2.0T TSI engine commonly sets P0299 due to a failed diverter valve (recirculating bypass valve) or a torn turbo inlet pipe. The diverter valve diaphragm tears from heat and age, causing boost to vent when it shouldn't. Check the diverter valve by removing it and pressing the diaphragm -- if it moves freely without vacuum, it is torn. Upgrade to the revised piston-type diverter valve for durability.
Labor: 30 min - 1 hour2011-2019 Chevrolet Cruze/Malibu 1.4T/2.0T easy DIY
The Chevy Cruze 1.4L turbo has a plastic charge pipe that cracks from heat cycling, causing a massive boost leak and P0299. Inspect the charge pipe from the turbo to the throttle body for cracks, especially at the connection points. GM released an updated charge pipe in harder plastic. Also check the turbo wastegate actuator -- a stuck wastegate causes chronic underboost. The wastegate actuator rod should have minimal play.
Labor: 30 min - 1 hour2007-2017 BMW 335i/535i/X5 (N54/N55) hard DIY
BMW N54 twin-turbo engines are notorious for wastegate rattle and boost loss. The wastegate actuator arms wear and develop play, preventing the wastegate from closing fully. Check for wastegate rattle by revving the engine to 2,000 RPM and listening for a metallic rattle from the turbo area. BMW released revised wastegate actuators. On high-mileage N54 engines, the turbo charge pipe (known as the 'chargepipe') also cracks from heat and pressure.
Labor: 2-4 hoursFrequently Asked Questions
What causes turbo underboost?
The most common cause is a boost leak - a disconnected or cracked intercooler hose. Other causes include a stuck wastegate or failing turbocharger.
Can I drive with P0299?
You can drive short distances, but the vehicle will have significantly reduced power. Do not tow or carry heavy loads.
How do I check for a boost leak?
Use a boost leak tester: remove the turbo intake pipe, attach the tester, and pressurize to 15 psi. Listen and feel for air escaping from connections, hoses, and the intercooler.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0299 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
See All Codes & Fixes for Your Vehicle
Explore More
Was this helpful?
Share carcodefinder.com with a friend who needs to decode their check engine light.