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P0299 Code: What Does Turbo Underboost Condition Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0299 is a generic OBD-II diagnostic trouble code indicating an underboost condition.


This underboost condition code only applies if you have a turbo or supercharger system installed on your vehicle. Since this is usually a high performance modification, you generally won’t see it come up unless you are working on a customized vehicle or a sports car that comes stock with a turbo or supercharger. 

Code P0299 indicates  the Turbo or Supercharger "A" has excessively low output.

A turbo or supercharger output is integral to its function within a vehicle. Superchargers and turbochargers take gas directly from the exhaust pipe and force it back into the combustion chamber at high pressure.

This increases the amount of oxygen in the reaction and adds any combustible gases from the exhaust to the mix. This volatile combination increases engine performance and horsepower when engaged.

If the output is low, it means the turbocharger or supercharger is not pushing sufficient exhaust gas back to the intake system. The ECU in your vehicle looks for a specific range of boost, and when the low boost is detected by the ECU, it sets a P0299 code.


Fortunately, there are only a few reasons you will see a code P0299 on your vehicle:

  • There is a fault with the turbo or supercharger
  • The engine has low oil pressure
  • EGR (Emission Gas Recycler) system is faulty
  • Air or air intake blockage or leak
  • The boost pressure sensor is faulty


Here’s what you’ll notice about how your vehicle when you have P0299:

  • Check Engine Light is illuminated
  • Little to no difference in acceleration (even when turbocharger or supercharger is engaged)
  • Lack of power when accelerating
  • Your turbocharger or supercharger is noisier than usual or the sound cuts in and out


Here’s the proper method for diagnosing the cause of a P0299 code:

  • Your technician begins by hooking up a scan tool into the vehicle's OBD-II port and pulling a trouble code report.
  • Next, your technician notes all freeze-frame data, which stores information about what conditions the vehicle was under when the code was set. (i.e. what your engine and turbo/supercharger was doing when the code was stored).
  • Once they have an initial code report and freeze-frame data, your technician resets all codes and takes your vehicle for a test drive to see if the code recurs.
  • After the test drive, your technician performs a visual inspection of the turbo/supercharger system, air intake system, EGR system, and any other associated systems.
  • Upon completing the visual inspection, your technician uses their scan tool to check for proper boost pressure sensor readings.
  • Finally, your technician checks all mechanical systems in the turbo or supercharger, and the oil pressure and air intake system are checked for leaks or restrictions.

Common mistakes

A competent technician will run a careful step-by-step diagnostic process before recommending any repairs. When all steps are not followed in the proper order or are not completed at all, mistakes happen and unnecessary repairs soon follow.

The P0299 diagnostic trouble code presents with symptoms from many causes. Following the diagnostic steps properly and in the right order is important for accurate diagnosis.

How serious

A P0299 diagnostic trouble code points to some rather serious mechanical failures, especially if you just ignore the problem and assume it will go away when blockages clear on their own.

Mechanical noise or drivability concerns (low power/slow acceleration), then the vehicle needs to be in the shop as soon as you can get it there.

A malfunctioning or broken turbo/supercharger can cause severe and expensive engine damage if it isn’t repaired quickly.

What repairs can fix the code

Repair manuals
Repair manuals

Depending on the cause, you are likely to make one of the following repairs:

  • Turbo or supercharger replacement (an expensive fix)
  • Repairing of the intake system (moderately expensive)
  • EGR replacement (an expensive fix)
  • Boost pressure sensor replacement (less expensive fix_
  • Low engine oil pressure repair (could be as inexpensive as a couple engine seals, or as pricey as a head gasket replacement)


Turbochargers and superchargers are high performance modifications for any vehicle. They require regular monitoring and maintenance to keep them in optimal working order.

If you notice even the slightest problem or sudden drop in acceleration speed or power, get your turbocharger or supercharger checked out immediately. Despite the amount of power and boost they provide to your car, they are actually fairly delicate components that can be damaged by airborne debris in the intake system or debris buildup.

Bottom line, if you’re check engine light comes on when you are accelerating and you’re not getting the power you’re used to, get your car checked immediately.

Even minor problems with your turbocharger or supercharger can turn into serious problems and expensive repair costs if you don’t take care of them right away.

P0299 code: what does turbo underboost condition mean & how to fix it