P0299Turbocharger/Supercharger A Underboost Condition
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0299 means actual boost stays below target for a period although the control already demands more. Thresholds: GM petrol 30–55 kPa below target with the warning light in the first trip; GM diesels 10–50 kPa, two trips; Ford EcoBoost more than 4 psi (about 28 kPa) for 5 s with the wastegate already commanded fully closed; Ford diesels 30–40 kPa for 10–15 s, with a further underboost code P2263. Typical causes from manufacturer bulletins: a charge air leak, a wastegate that lost its preload or whose rod came off, a leaking bypass valve, sticking turbo vanes on diesels, and ice in the charge air cooler in winter. A faulty boost sensor can also fake underboost. Many engines then limit power.
- What you may notice
- Loss of power, sluggish acceleration
- Limp mode, power limited
- Check engine light on
- Whistling or hissing from the charge air path under load
- Likely causes
- LikelyLeak in the charge air path (hose off or torn, cooler leaking, clamps)
- LikelyWastegate faulty (rod off, preload lost, vacuum or solenoid, diaphragm)
- PossibleTurbo vanes sticking or turbo worn (diesel)
- PossibleBypass valve leaking (torn diaphragm) or its control
- RareIce in the charge air cooler, boost sensor or connector, or software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.