TrustThisCar

P0299: Turbocharger or Supercharger Underboost Condition

The engine asked the turbocharger for a certain boost pressure and measured less than it expected. The car responds by cutting power to protect itself, which is why this code is usually noticed as the car suddenly refusing to pull. The leak or the stuck part is often somewhere cheap, but the diagnosis takes time.

Severity
Serious
Safe to drive
No
Typical repair
£85 to £1800
System
Engine and fuel

What P0299 means

The engine asked the turbocharger for a certain boost pressure and measured less than it expected. The car responds by cutting power to protect itself, which is why this code is usually noticed as the car suddenly refusing to pull. The leak or the stuck part is often somewhere cheap, but the diagnosis takes time.

The code is stored by the engine control unit the moment the reading falls outside the range the manufacturer allows. Stored is not the same as diagnosed: P0299 names the symptom the car detected, not the part that caused it. That is why the repair figures below sit in a range rather than at a single price.

What causes it

In rough order of how often each one turns out to be the culprit:

  1. A split or detached intercooler hose or boost pipe, the cheapest outcome and a common one
  2. A sticking variable-geometry mechanism on the turbo, seized with soot
  3. A failed boost pressure sensor or a blocked sensing line
  4. A leaking or disconnected vacuum line to the turbo actuator
  5. A worn turbocharger with excessive shaft play, the expensive outcome
  6. A blocked particulate filter raising back pressure enough to limit boost

What you notice from the driver's seat

How much P0299 costs to fix

Parts cost roughly the same wherever you are. What moves the total is the shop rate, which is why the same job is two to three times the price in the United States that it is in Italy. These figures assume an independent workshop, not a franchised dealer, and cover the cheapest and the most expensive of the causes listed above.

Indicative repair cost for P0299, independent workshop
CountryPartsLabourTotal
United States $25 to $1500 $95 to $840 $120 to $2350
United Kingdom £20 to £1250 £65 to £560 £85 to £1800
Germany €25 to €1400 €80 to €700 €100 to €2100
Italy €25 to €1400 €35 to €320 €60 to €1700

Based on 0.8 to 7.0 hours of book labour at local shop rates, plus parts at local retail. Indicative ranges, not quotes.

Can you keep driving?

No. Driving on with this fault risks further damage, so the car should be recovered rather than driven.

Will it fail an MOT or emissions test?

Usually yes, because the warning light will be on, and an illuminated engine light fails the visual part of the check in every market we cover.

Clearing the code the day before a test is a false economy: erasing the memory also resets the readiness monitors, and a car that arrives with its monitors incomplete is refused on that ground alone in most testing regimes.

If you are looking at a used car with P0299

Treat this one as a reason to walk away unless the seller has a recent invoice for the repair. It is expensive, it does not fix itself, and a seller who has lived with it for months has probably left other things alone too.

The thing worth checking is not the code on its own. It is whether the memory was cleared recently. Every car keeps two numbers alongside the fault list: the distance travelled since the codes were last erased, and the state of the readiness monitors. A car with no stored faults, incomplete monitors and 30 km since the last reset was wiped in the seller's driveway, probably this week. That combination tells you more than any single code does.

TrustThisCar reads all of it during the viewing, in three minutes, with the kind of Bluetooth adapter that costs about 20 euro: stored, pending and permanent codes, readiness monitors, distance since the last reset, and a verdict in plain words you can send to the seller while you are still standing next to the car.

Check a car before you buy it

Questions people ask about P0299

What does code P0299 mean?

The engine asked the turbocharger for a certain boost pressure and measured less than it expected. The car responds by cutting power to protect itself, which is why this code is usually noticed as the car suddenly refusing to pull. The leak or the stuck part is often somewhere cheap, but the diagnosis takes time.

Can I drive with a P0299 code?

No. Driving on with this fault risks further damage, so the car should be recovered rather than driven.

Will P0299 fail an emissions test or MOT?

Usually yes, because the warning light will be on, and an illuminated engine light fails the visual part of the check in every market we cover.

How much does it cost to fix P0299?

It depends on the shop rate where you live: United States $120 to $2350, United Kingdom £85 to £1800, Germany €100 to €2100, Italy €60 to €1700. Parts are close to the same everywhere; labour is what moves the total.

Codes that often show up with this one

Last reviewed 2026-10-03.