OBD-II Code · Powertrain
P0299
Turbocharger/Supercharger Underboost
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$80–$3,500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Boost pressure is below the commanded minimum. Common on turbo diesels and modern gas engines.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Loss of power
- Reduced fuel economy
- Possible limp mode
Likely causes
- Boost leak (cracked hose or intercooler)Most common
- Stuck wastegate
- Failed turbo
- Faulty boost sensor
- Clogged catalyst
Read the full diagnostic procedureP0299 is a turbocharger underboost code, set when actual manifold pressure falls below commanded boost by a calibrated margin, typically 2 to 4 psi u…
P0299 is a turbocharger underboost code, set when actual manifold pressure falls below commanded boost by a calibrated margin, typically 2 to 4 psi under target for several seconds under load. Cheapest and most productive first step is a smoke test of the entire boost tract from turbo outlet through intercooler to throttle body; pressurize to 10 to 15 psi with a smoke machine and look for leaks at intercooler end-tanks, couplers, charge pipe clamps, and the throttle body gasket. Most P0299 faults are boost leaks, not failed turbos. Next, scan live data and graph commanded versus actual boost during a wide-open-throttle pull; an underboost of 3 to 5 psi with no audible leak points to wastegate or boost-control solenoid issues. Test the wastegate actuator by commanding it bidirectionally on the scan tool or applying vacuum or pressure manually; the rod should move smoothly through full travel. A wastegate stuck partially open will not hold boost. Also check the boost control solenoid for proper PWM and physical operation.
Caveat
a partially clogged catalytic converter or DPF can cause underboost by raising back pressure and reducing turbine flow, mimicking a turbo fault.
Vehicle-specific patternsFord EcoBoost 2.0L, 2.3L, and 3.5L (2013-2020 Fusion, Escape, Edge, F-150) commonly sets P0299 from cracked intercooler hoses and split charge pipe c…
Ford EcoBoost 2.0L, 2.3L, and 3.5L (2013-2020 Fusion, Escape, Edge, F-150) commonly sets P0299 from cracked intercooler hoses and split charge pipe couplers, and from condensation freezing in the intercooler during cold operation, addressed in Ford TSB 17-2174 with an air deflector kit. VW/Audi 2.0T TSI (2008-2017 GTI, A4, Tiguan) sees P0299 from torn diverter valve diaphragms (the carbon revision is the common fix) and from PCV-related boost leaks.
- 2008-2014Subaru WRX and Forester XT EJ255 sets P0299 from cracked intercooler Y-pipes and silicone couplers, as well as boost control solenoid failure. BMW N54 (2007-2010 335i) sees P0299 from wastegate rattle and bypass valves leaking, often paired with P0234.
Estimated repair$40 to $2,500.
Look up another code
P0299 — frequently asked
What does a P0299 code mean?
Boost pressure is below the commanded minimum. Common on turbo diesels and modern gas engines.
What causes a P0299 code?
Common causes: Boost leak (cracked hose or intercooler); Stuck wastegate; Failed turbo; Faulty boost sensor; Clogged catalyst.
What are the symptoms of a P0299 code?
Typical symptoms: Check engine light; Loss of power; Reduced fuel economy; Possible limp mode.
Is it safe to drive with a P0299 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $80-$3,500.
How do I diagnose a P0299 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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