What it means
The control module detected boost pressure below the expected level. Possible causes include leaks, a turbocharger or supercharger fault, or a control problem; the code alone does not identify the failed part.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The control module compares requested boost with measured intake pressure to assess turbocharger or supercharger A performance. P0299 sets when measured boost stays below the expected level, which can come from a charge-air leak, a boost-control fault, or a failed forced-induction unit.
Common causes
Most likely first.
- Leak in a charge-air hose or intercooler
- Boost control or wastegate fault
- Turbocharger or supercharger fault
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Review freeze-frame data and requested-versus-actual boost readings, along with any air-flow, pressure, or boost-control codes.
- With the engine off, inspect the charge-air hoses, clamps, and intercooler for splits, loose joints, or signs of escaping air.
- Inspect the wastegate or other boost-control hardware and its hoses, wiring, or actuator connections for visible damage or disconnection.
- Check pressure-sensor readings and boost-control operation using the manufacturer’s procedure before replacing parts.
- If the intake path and controls pass inspection, test the turbocharger or supercharger for mechanical damage or leakage as specified by the manufacturer.
Common fixes
- Refit or replace a split charge-air hose and secure loose clamps.
- Repair damaged boost-control hoses, wiring, or actuator connections.
- Replace a confirmed faulty boost-pressure sensor or control component.
- Repair or replace the turbocharger or supercharger only after testing confirms a unit fault.
Can I keep driving?
With substantial power loss, avoid overtaking, steep climbs, and heavy acceleration; stop if the engine runs roughly or smoke becomes heavy. Continued operation with a boost fault can worsen engine or turbocharger damage, and blue or black smoke warrants prompt attention.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.