P0299 fault code: turbo boost pressure too low
Plain-language definition
Turbocharger/Supercharger A Underboost Condition
What does it mean?
A turbo is spun by the force of the exhaust gas and pushes more air into the engine than it would normally get; this extra pressure is called boost (charge) pressure. The engine computer calculates how much boost it wants based on the accelerator pedal position and engine speed, and measures the pressure actually produced with a sensor on the intake side. The same code is also used on engines with a mechanical compressor (supercharger).
P0299 is stored when the measured pressure stays clearly below the requested value for a set time; in other words, the engine isn't getting as much air as it expects. The letter A in the definition refers to the first turbo on engines with more than one turbo; on cars with a single turbo, the code also appears under this name.
Along with this code, you may notice a clear drop in power, with the car lacking pull, especially when accelerating and going uphill. On many cars the engine computer may limit power to protect the engine (limp mode). A whistling or hissing noise from the turbo, black smoke from the exhaust and higher fuel consumption are also possible.
How serious is it?
It's a Warning-level code. The cause can be as simple as a loose clamp or as serious as the turbo itself, so how serious it is depends largely on the cause.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- A crack, loose clamp or air leak in the hoses between the turbo and the engine or in the intercooler
- The vanes of a variable-geometry turbo (VGT) sticking because of soot, or the wastegate (bypass valve) not working properly
- A problem with the control valve (solenoid) that manages boost pressure, or with the vacuum hoses
- The boost pressure sensor giving wrong readings
- A clogged air filter or a restriction in the exhaust (e.g. an overloaded DPF)
- A worn or damaged turbo
The list shows general causes; a workshop finds the actual cause on your car with a check.
Related codes
How does it appear in the 2dakika report?
Turbocharger/Supercharger A Underboost Condition
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.