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.
Medium severity. Can I keep driving?You can normally reach a repair shop with the car in its limited state, avoiding passing and demanding highway driving. If you see blue smoke, hear a loud new whistle, or the oil level drops, do not continue, because the turbo may be failing.
Symptoms
- Loss of power, sluggish acceleration
- Limp mode, power limited
- Check engine light on
- Whistling or hissing from the charge air path under load
Most likely causes
- Leak in the charge air path (hose off or torn, cooler leaking, clamps)
- Wastegate faulty (rod off, preload lost, vacuum or solenoid, diaphragm)
- Turbo vanes sticking or turbo worn (diesel)
- Bypass valve leaking (torn diaphragm) or its control
- Ice in the charge air cooler, boost sensor or connector, or software
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P0299 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- 99: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0299?
You can normally reach a repair shop with the car in its limited state, avoiding passing and demanding highway driving. If you see blue smoke, hear a loud new whistle, or the oil level drops, do not continue, because the turbo may be failing.
What causes code P0299?
The most common causes are: leak in the charge air path (hose off or torn, cooler leaking, clamps); wastegate faulty (rod off, preload lost, vacuum or solenoid, diaphragm); turbo vanes sticking or turbo worn (diesel).
Related codes
- P0234Turbocharger/Supercharger A Overboost Condition
- P2263Turbocharger/Supercharger A Boost System Performance
- P0236Turbocharger/Supercharger Boost Sensor A Circuit Range/Performance
- P0238Turbocharger/Supercharger Boost Sensor A Circuit High
- P0033Turbocharger/Supercharger Bypass Valve A Control Circuit
- P259ETurbocharger A Boost Control Position At Low Limit
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
- gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.