P0299 on Audi: How to Diagnose & Fix
Turbo/Supercharger Underboost Condition
10 Audi models · 11 documented issues · 7 critical · $300-$5,000 repair
P0299 on Audi by model: symptoms, diagnosis and fix
The BorgWarner BV43 variable-geometry turbocharger (OEM part 03L253056, BorgWarner 53039880208) can fail due to oil starvation, bearing wear, or variable geometry vane sticking/seizing. The most common failure mode is the variable vanes sticking or seizing, causing overboost or underboost. Catastrophic failures (compressor shaft snapping) are less common but documented. Failures typically occur around 100,000-150,000 miles.
Common Symptoms
- Loss of power
- Excessive black smoke
- Turbo whine or grinding
- Check engine light with boost codes
- Oil in intercooler
- Overboost shutdown (limp mode)
- Turbo actuator fault codes
How to Fix
Regular oil changes with VW 507.00 spec diesel oil are critical - the turbo depends on clean oil for bearing lubrication. Replace the turbo if it has failed, using the OEM BorgWarner unit (03L253056). Always replace the turbo oil feed line (03L145771) and oil return line (03G145736F) with new gaskets (03L145757Q oil return gasket) when replacing the turbo. Let the engine idle 30-60 seconds before shutdown to allow the turbo to cool down.
Sources for this issue (1)
The 2014-2017 SQ5 uses the supercharged 3.0 TFSI V6 (EA837), the same engine family as the B8 S4/S5 and the C7 A6/A7 3.0T. A Roots-type (Eaton-made) supercharger sits in the valley of the V6 and is belt-driven from the crankshaft. Two parts of that system wear with mileage. Supercharger nose-cone (snout) bearing: this front bearing supports the supercharger drive shaft and carries constant load from the drive belt. As it wears it makes a whine or grinding noise that rises with engine RPM. Early on you may only hear it at cold start or under light load; as it gets worse the noise becomes constant and louder, and it can progress to boost loss. A specialist shop puts typical wear at roughly 100,000-160,000 km, and a parts supplier's guide says 80,000-130,000 miles. If it is ignored, the shop warns, a failed bearing can let the rotors make contact, destroying the supercharger and sending metal debris into the intake. Charge-air (intercooler) cooling circuit: the supercharger uses a water-to-air intercooler on its own coolant circuit with an electric pump. When the pump fails, intake air temperatures rise and performance drops, which is most noticeable in hot weather. The lines and fittings in this circuit can also leak. A related failure with the same symptoms is a leaking intercooler core: one tuner says the brazing in the cores can fail, causing high intake air temperatures, coolant loss, or air that keeps returning after the system is bled.
Common Symptoms
- Whine or grinding from the supercharger that rises with RPM, often first at cold start or light load
- Play in the supercharger drive shaft
- Supercharger belt squeal or chirp on acceleration
- Reduced boost or power loss, especially in hot weather
- Intercooler pump fault code
- Elevated intake air temperatures
- Low coolant or seepage around the supercharger
How to Fix
What to check first: 1. Whine or grind: work out whether the noise comes from the supercharger snout or from the belt. With the engine off, pull the supercharger drive shaft back and forth; any play points to a worn nose-cone bearing. A squeal or chirp from the front of the engine on acceleration, or a loose or frayed belt, points to the belt or tensioner instead. 2. Power loss when hot: check for stored fault codes (including an intercooler pump code), log intake air temperature on a drive, and check that the intercooler pump is working. Check the coolant level and look for seepage around the supercharger. If coolant keeps dropping or air keeps returning after bleeding, suspect a leaking intercooler core. Repairs: - Worn snout bearing: if it is caught early, a shop can replace the nose-cone bearing (for example with an aftermarket rebuild kit or upgraded bearing) without removing the whole supercharger. If the shaft already has play, the usual fix is a new or factory-remanufactured supercharger. One guide suggests inspecting the nose cone about every 60,000 miles. - Belt: replace the supercharger belt if it is loose or frayed. Integrated Engineering lists the factory belt as part number 06E903137T. One shop recommends replacing the belt and tensioner every 80,000-100,000 km. - Intercooler circuit: replace a failed intercooler coolant pump, repair any leaking lines or fittings, and replace leaking intercooler cores, then bleed the circuit. Coverage: the cited sources do not mention an Audi recall, service bulletin or warranty extension for these parts. Cost: the cited sources give no dollar figures. One shop quotes each job after diagnosis and describes belt and tensioner service as routine, an early bearing repair as moderate, and a full supercharger replacement as the expensive outcome.
Sources for this issue (3)
- Foreign Automotive - Audi 3.0T Supercharger Problems: Nose Cone Bearing, Intercooler Pumprepair-shop
- Euro Premium Parts - Audi EA837 Engine Guide (SQ5 8R): Supercharger Nose Cone Bearing Failurearticle
- Integrated Engineering - 3.0T Supercharged Engine Health Checklist (8R SQ5): Supercharger Snout Bearingarticle
Audi identifies coolant loss from the mechanical coolant pump on 2018-2024 SQ5 V6 TFSI models. In some cases P0299 is logged when coolant entering the vacuum system impairs changeover valve N649. Audi cautions that a small trace on the pump drip cup can be normal and that dried deposits at the vacuum connection alone do not confirm a leak.
Common Symptoms
- Coolant loss or visible coolant leak
- Coolant warning lamp
- Engine warning lamp
- P0299 underboost in some cases
How to Fix
For an applicable vehicle, follow Audi TSB 2070349/4 and current workshop information. Locate the leak precisely: clean and dry the area, fill the cooling system, check for leakage at idle and up to about 2,500 rpm, and test the cooling system as the workshop manual specifies. If no further leak is found, Audi says to keep observing without replacing parts; if the leak returns, replace the leaking component. Where P0299 is logged, the bulletin attributes it to switch valve N649 contaminated with coolant from a leaking pump, so have that secondary damage assessed.
Sources for this issue (1)
The S8 4.0T V8 shares coolant line issues with other 4.0T Audi models (Audi TSB 2036167 covers the 2013-2014 S6, S7, A8 and S8). Heat after shutdown can damage the O-rings at the turbocharger coolant feed and return pipe connections, causing slow coolant loss and encrusted coolant residue on the turbocharger flange.
Common Symptoms
- Low coolant level light
- Coolant level too low
- Black, encrusted coolant residue on the turbocharger coolant lines
How to Fix
Replace the O-rings on the turbocharger coolant supply and return pipes with Audi's optimized temperature-resistant O-rings (the correct size depends on the pipe's O-ring groove; replacing the pipes themselves is not allowed per the TSB), and update the engine control module software (SVM code 01A225) if required. Refill and bleed the cooling system per Audi procedure. Monitor coolant levels closely.
Sources for this issue (1)
The water-to-air intercooler system on the S5 3.0T uses an electric coolant pump that can fail, causing elevated charge air temperatures and reduced power. Heat soak becomes severe in warm climates.
Common Symptoms
- Heat soak power loss
- Reduced boost performance
- Intercooler pump fault code
- Elevated intake temps
- Sluggish acceleration in heat
- Check engine light
How to Fix
Replace intercooler coolant pump. Check intercooler lines for leaks and flush the circuit during replacement.
Sources for this issue (1)
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 Audi?
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 Audi it is documented across 10 models: A3, SQ5, S8, S5, A6, Q8, S7, RS5, A1, A7.
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 Audi?
Published repair estimates on Audi range from $300 to $5,000 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.