P0299
Turbocharger/Supercharger "A" Underboost Condition
Moderate· Fix soonIntermediatePowertrainGeneric, all makes
What it means
The turbo is not producing as much boost as the ECU expected. The most common cause is a boost leak in the intercooler pipes.
Is it safe to drive?
Usually drivable with reduced power. Avoid heavy loads. If you hear loud whining or see blue smoke, the turbo itself may be failing; stop driving.
Symptoms
- Loss of power
- Limp mode
- Whistling or whooshing sound (boost leak)
- Black smoke on diesels
Probable causes
Most likely first
- 1Split intercooler hose or loose clamp (very common)
- 2Leaking intercooler
- 3Wastegate stuck open
- 4Sticking VGT vanes (diesel)
- 5Faulty boost control solenoid or vacuum line
- 6Worn turbocharger
- 7Clogged air filter or DPF
How to diagnose it
Work through these in order before buying parts
- 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
- 2Inspect all intercooler hoses and clamps for splits and oil residue.
- 3Pressure-test the intake (boost leak test).
- 4Compare desired and actual boost on live data.
- 5Check wastegate or VGT actuator movement.
- 6Check turbo shaft play and look for oil in the intake.
- 7Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.
Common fixes
- Replace split hoses and clamps
- Repair or replace the intercooler
- Free up the VGT vanes or wastegate
- Replace the boost control solenoid
- Replace the turbocharger
Videos about P0299
This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.