P0299 Turbo or Supercharger Underboost
Get it checked soon
The engine is not getting the boost pressure the computer asked for. A leaking intercooler hose or clamp is the usual cause; a stuck wastegate or a worn turbo is less common. Expect less power, and get it checked soon.
- Safe to drive?
- Yes, gently, fix soon
- Typical cost at a shop
- $77-$3,068 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
Watch boost and the pressure sensors live to tell a boost leak from the wastegate or a sensor.
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Codes and live sensors are free in the app. Obie, the AI mechanic, is part of ScanMyCar Pro.
What it means
A turbocharger or supercharger pushes extra air into the engine for more power. The computer sets a target boost pressure and measures what it gets. P0299 means the measured boost stayed below the target. Air escaping between the turbo and the engine is the most common reason.
The technical version
The computer compares desired boost with the boost or manifold pressure sensor reading. P0299 sets when the actual pressure stays below the target by more than a set margin for a set time. Boost leaks, a wastegate stuck open or a sticking actuator, a faulty boost control solenoid, a restricted intake or exhaust, a worn turbo and a faulty pressure sensor can all cause it.
Official name: Turbocharger/Supercharger "A" Underboost Condition.
Symptoms
- Less power, especially when you accelerate hard.
- Reduced-power mode or a warning message.
- A whoosh or hiss under boost.
- Sometimes more smoke or a new turbo noise.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A boost leak: a split intercooler hose, loose clamp or cracked intercooler | most common | Oil film or a loose clamp on the charge pipes; a hiss under load. |
| A wastegate stuck open or a faulty actuator or boost control solenoid | common | Boost stays low at all loads; actuator or solenoid fault codes. |
| A restricted air filter or intake | less common | A blocked filter or collapsed intake hose. |
| A worn or damaged turbo | less common | Shaft play, oil in the intake, whining or grinding. |
| A faulty boost or manifold pressure sensor | less common | Its reading does not match a gauge or the engine-off barometric value. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Many cars show desired and actual boost, or manifold absolute pressure, with barometric pressure. On a steady full-throttle pull in a safe place, actual boost should follow the desired value closely. A large gap under load points to a leak or a wastegate; a sensor that does not read barometric pressure with the engine off points to the sensor.
What to check first, in order
-
Inspect the charge pipes, hoses, clamps and intercooler.
Boost leaks are the most common cause.
What the data shows: No reading needed.
Cost: free to look
-
Check the air filter and intake for blockages.
A cheap check.
What the data shows: No reading needed.
Cost: $77-$97 at a shop (Air filter replacement, RepairPal)
-
Compare desired and actual boost under load, and the sensor reading with the engine off.
It separates a leak from a sensor fault.
What the data shows: Actual should track desired; engine off, the sensor should read about barometric pressure.
Cost: no cost if you have a scanner
-
Replace a split intercooler hose or pipe.
A common fix.
What the data shows: Boost reaches the target again.
Cost: $603-$671 at a shop (Turbocharger intercooler tube replacement, RepairPal)
-
Have the wastegate, boost solenoid and turbo checked.
If there is no leak.
What the data shows: Not a scanner step.
Cost: $2,490-$3,068 at a shop (Turbocharger assembly replacement, RepairPal)
Is it safe to drive?
Get it checked soon
Yes, gently, fix soon. Most cars cut power to protect the engine; a failing turbo can get worse fast.
Usually drivable gently. Many cars go into a reduced-power mode, which makes merging and passing harder. A simple boost leak does no harm on its own, but a turbo that is failing can shed parts or burn oil and damage the engine, so stop if you see smoke or hear new turbo noises.
Stop driving and get help if
- Blue or heavy white smoke comes from the exhaust.
- You hear a loud whine, siren or grinding from the turbo.
- The oil pressure light comes on or you see oil leaking from the turbo area.
What it costs
| Repair | Typical cost |
|---|---|
| Check engine light diagnosis (shop)RepairPal, updated September 3, 2026 | $125-$183 |
| Air filter replacementRepairPal, updated June 18, 2026 | $77-$97 |
| Turbocharger boost sensor replacementRepairPal, updated June 18, 2026 | $225-$261 |
| Turbocharger intercooler tube replacementRepairPal, updated June 18, 2026 | $603-$671 |
| Turbocharger assembly replacementRepairPal, updated June 18, 2026 | $2,490-$3,068 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated June 18 and September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner.
Can I clear it? Will it come back?
After the repair, clear the code and drive with some firm acceleration in a safe place. If boost reaches its target and the code stays away, the fix worked.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Related codes
Also related, no guide yet: P0234, P0236.
How Obie handles P0299
Obie compares desired and actual boost with the pressure sensors and tells you whether the pattern points to a leak, the wastegate or a sensor. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Is P0299 a bad turbo?
Usually not. A boost leak from a hose or clamp is more common. Check those first.
Can I drive with P0299?
Gently, for a short time. Stop if you see smoke or hear new noises from the turbo.
Why is my car in limp mode with P0299?
Many cars cut power when boost is low, to protect the engine and the turbo.
Sources
- RepairPal: Check engine light diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Air filter replacement (updated June 18, 2026) repairpal.com
- RepairPal: Turbocharger boost sensor replacement (updated June 18, 2026) repairpal.com
- RepairPal: Turbocharger intercooler tube replacement (updated June 18, 2026) repairpal.com
- RepairPal: Turbocharger assembly replacement (updated June 18, 2026) repairpal.com
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0299 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.