Fuel & air metering · Powertrain · generic (SAE-defined)
P0299: Turbocharger/Supercharger "A" Underboost Condition
P0299 means the turbocharger or supercharger is producing less boost pressure than the engine computer requested, usually because of a leak, a wastegate problem, or a worn turbo.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0299 sets
The powertrain control module (PCM) compares commanded boost with actual boost from the boost or manifold absolute pressure (MAP) sensor. If actual boost stays below the desired value by a calibrated margin for a set time, P0299 sets. The thresholds and enabling conditions differ by manufacturer.
Common causes of P0299
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Boost leak from a loose or split intercooler hose or clamp
- Cracked intercooler or leaking intake connection
- Wastegate stuck open or a faulty wastegate control solenoid
- Leaking or failed bypass/diverter valve
- Worn or damaged turbocharger
- Restricted air filter or exhaust restriction
- Faulty boost or MAP sensor
P0299 symptoms
- Check engine light on
- Noticeable loss of power, especially when accelerating
- Reduced power or limp mode
- Hissing or whooshing noise under boost
- Excess smoke or oil in the intake if the turbo is failing
How P0299 is diagnosed
- Review freeze frame data for desired and actual boost at the time of the fault.
- Check for related codes such as boost sensor, wastegate, or airflow codes.
- Visually inspect charge pipes, intercooler, and clamps for oil residue or looseness.
- Smoke-test or pressure-test the intake and charge air system for leaks.
- Verify wastegate and bypass valve operation with a scan tool or vacuum pump.
- Inspect the turbo for shaft play, damaged blades, or oil leaks.
Typical fixes for P0299
- Replace a leaking intercooler hose or clamp
- Replace the wastegate solenoid, actuator, or bypass valve
- Repair a cracked intercooler
- Replace a faulty boost or MAP sensor
- Replace or rebuild a worn turbocharger
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
P0299 is commonly reported on small-displacement turbocharged gasoline engines and on turbodiesels, where wastegate linkage wear, bypass valve failures, and charge pipe leaks are frequent causes.
Related codes & warning lights
P0299 FAQ
What does code P0299 mean?
P0299 means the turbocharger or supercharger is producing less boost pressure than the engine computer requested, usually because of a leak, a wastegate problem, or a worn turbo. The standard definition is "Turbocharger/Supercharger "A" Underboost Condition."
Can I drive with a P0299 code?
Generally yes for short trips, though power will be reduced and limp mode is possible. Diagnose it within days, because a failing turbo can shed debris or leak oil into the intake.
Is P0299 always a bad turbo?
No. Boost leaks from hoses and clamps and wastegate control faults are frequent causes and should be ruled out before replacing the turbocharger.
Can cold weather trigger P0299?
On some engines, yes. Condensation or icing in the charge air system and sticky wastegate linkages can cause underboost in cold conditions.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.