Audi P0299

Turbo underboost on Audi — on 2.0 TFSI it's PCV/diverter valve, on 2.0/3.0 TDI it's the VGT actuator or charge pipe leaks.

Audi P0299 — Turbo underboost on Audi — on 2.0 TFSI it's PCV/diverter valve, on 2.0/3.0 TDI it's the VGT actuator or charge pipe leaks. Typical UK independent garage cost: £180–£1600.

What actually causes P0299 on a Audi

On 2.0 TFSI the typical cause is a torn PCV diaphragm or a failed diverter valve — both create a boost leak the ECU interprets as turbo underperformance. On 2.0 TDI CR it's usually carbon-stuck VGT vanes or a split intercooler hose. On 3.0 TDI it's swirl flap motor failure or a cracked plastic intake manifold. Audi diesels also throw P0299 when the EGR cooler bypass valve sticks.

Audi engines that log P0299

• 2.0 TFSI EA113/EA888 (A3, A4, A5, TT)
• 2.0 TDI CR (A3, A4, A6)
• 3.0 TDI V6 (A4, A6, A8, Q5, Q7)
• 1.4 TFSI

How we diagnose P0299 on a Audi

1. Smoke-test the full intake tract from turbo outlet to inlet manifold
2. On 2.0 TFSI, inspect PCV valve diaphragm (top of cam cover) — common failure
3. On 2.0/3.0 TDI, scan tool: monitor VGT vane position vs commanded under load
4. Check intercooler hoses for splits, particularly the rubber elbows
5. Test diverter valve (TFSI) by pulse-testing with scan tool actuator function

The common misdiagnosis to avoid

Don't replace the turbo on a 2.0 TFSI without first smoke-testing the intake and checking the PCV — a £45 PCV valve cures countless P0299 codes on Audis.

Audi P0299 repair cost in the UK

Expect £180–£1600 including parts and labour at an independent garage. Main-dealer quotes on Audi are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

On 2.0 TFSI EA888 engines, the cam cover (with integrated PCV) is sold as a complete unit by VAG — £230 fitted by a specialist solves the boost issue and stops the oil burning that often comes with it.

Codes usually seen alongside P0299 on Audi

• P2015
• P0234
• P132B
• P2279

Symptoms drivers report with P0299

• Loss of power above 2,000–2,500 RPM — car feels flat overtaking on the motorway
• Limp mode kicks in at 3,000 RPM, resets after a key cycle, then returns within 10 miles
• Distinctive 'tappet-like' rattle at idle on 1.4 TSI = wastegate actuator rod play
• Whistling from engine bay under load — split intercooler pipe or Y-piece
• Black smoke or fuel smell from the exhaust on diesels — VNT stuck open, over-fuelling
• Paired codes: P0234 (overboost, VNT stuck closed), P0299 with P0401 (EGR + boost overlap), P0299 with P132B (turbo boost control)

Repairs that clear P0299

• Smoke-test the boost system first (cheap and finds most causes)
• Clean VNT vanes with rocker-arm actuation
• Replace boost sensor
• Replace turbo as last resort

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0299 guide.

Reading P0299 on a Audi properly

A generic reader will show P0299 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Audi has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0299 without fixing it

Erasing the code resets the Audi's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0299 is showing on your Audi, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.