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