What P0299 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.
On forced-induction engines the engine computer commands a target boost pressure and measures what it gets. Overboost means pressure exceeded the target; underboost means the system could not reach it.
What “Underboost” means here
The system could not reach the commanded boost. Typical directions: a leak in the charge piping or intercooler, a wastegate stuck open, a restricted intake or exhaust, a variable-vane turbo sticking, or a turbocharger that is worn.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0299:
- Loss of power or limp-home mode
- Whistling or hissing under load if a hose has split
- Surging or jerky power delivery
Where to start diagnosing P0299
- Inspect intercooler pipes and hoses for splits and loose clamps; a leak is a common cause of underboost.
- Check the wastegate or variable-vane actuator moves freely and the control vacuum or electrical signal is reaching it.
- Compare desired and actual boost in live data during a controlled pull.
- Listen and feel for turbo shaft play or damage.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0299. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Intake manifold absolute pressure (PID 0x0B) | Shows boost above atmospheric pressure. |
| Boost pressure control (PID 0x70) | Where supported, desired vs actual boost. |
| Engine load (PID 0x04) | Context for the boost reading. |
Related codes
Codes from the same turbocharger / supercharger boost control family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0234 | Turbocharger/Supercharger "A" Overboost Condition |
Further reading
Frequently Asked Questions
What does P0299 mean?
P0299 is the generic SAE J2012 code for "Turbocharger/Supercharger "A" Underboost Condition". In plain terms, it means the engine computer's turbocharger / supercharger boost control monitor has reported "Turbocharger/Supercharger "A" Underboost Condition".
Can I keep driving with P0299?
Overboost can damage an engine; underboost usually just costs power. Avoid hard acceleration until it is checked.
What should I check first for P0299?
Inspect intercooler pipes and hoses for splits and loose clamps; a leak is a common cause of underboost.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.