P0299 CODE: Causes and Fixes, Turbo / Supercharger Underboost Condition

The engine code p0299 is another common trouble code that you will encounter with your vehicle. If you are not familiar with it, it is so easy to get lost with it, even causing further damage as you attempt to fix the problem yourself. 

No worries, my years of experience as an auto technician has exposed me to these types of problems. I am here to help you out. Still, it is best to be guided with a professional if you are not confident with your fixing skills.

What Causes the Diagnostic Code p0299?

For one, the p0299 is an OBD2 trouble code that simply indicates an underboost condition. This means that it is only triggered if your vehicle is installed with a turbocharger or a supercharger system. Because this modification is usually high performance, you will not see it occurring unless you have a sports car or a customized vehicle that features a turbocharger or a supercharger.

The following summarizes the potential causes of code p0299 error:

  • Faulty MAP sensor
  • Open, burnt or shorted MAP sensor wires
  • Corroded, loose, bent or disconnected pins in the MAP sensor wiring
  • Faulty boost pressure sensor
  • Open, burnt or shorted boost pressure sensor wiring
  • Corroded, loose, bent or disconnected pins in the boost pressure sensor wires
  • Restricted or clogged air filter
  • Air leaks in the Intake Manifold
  • A leak in the Exhaust Manifold
  • Lacking fuel pressure system
  • Clogged or faulty MAF ( Mass Air Flow ) sensor
  • Faulty turbocharger or supercharger
  • Faulty control solenoid(s) of the turbocharger or supercharger

  • What are the Symptoms of the OBD2 Code p0299?

    The following are among the most common symptoms when engine code p0299 is triggered:

  • Poor fuel economy
  • Check Engine Light is lit
  • Possibility of engine misfires
  • Increase in emissions
  • Poor engine performance (particularly at wide-open throttle acceleration)
  • Possibility of a whining noise coming from the turbocharger/supercharger

  • How to Diagnose the p0299 Code

    Before performing this diagnostic and troubleshooting procedure, it is highly recommended to make sure that you have at least some basic knowledge regarding safety precautions as you work on your auto.

    1. Let’s Get Started!

    In order to eliminate a possible condition in the intermittent DTC, it is recommended to clear ECY memory. Afterward, you can perform a complete driving cycle. While doing so, you can read and note the different data trouble codes. After taking note of them, clear the memory and perform a complete driving cycle for at least 5 to 10 minutes.

    If you notice that the Check Engine Light is off, you may be encountering an intermittent issue. If you notice that during the driving cycle, the light is lit, then you can move forward with the diagnostic procedure. 

    2. Visual Check

    • Check the condition of the MAF

    In order to check the condition of the MAF, there is a need to detach it first from the vehicle. This is a very important sensor that needs to be diagnosed and cleaned.

    Do a thorough visual check of the MAP connector and wiring. See if there are damaged, burnt, deteriorated or corroded wires. You can also want to unplug the sensor first, looking for loose connections, bent terminal pins, and other indications of having a bad connection.

    • Check the vacuum hoses

    Conduct a thorough visual check on all vacuum lines, PCV, MAP sensor, fuel pressure regulator, brakes vacuum booster, and others. You may also want to look into the air intake hose while checking for signs of leak and deterioration.

    • Check the exhaust pipe/manifold

    Leaks that are present in the exhaust, particularly the one just before the system’s turbocharger, may result in a decrease in the boost pressure. This is a reason why it is very important to check the condition of the exhaust pipe, repairing any leak, such as a faulty exhaust manifold.

    • Check the air filter

    A clog in the air filter can significantly decrease the boost pressure in the turbocharger and supercharger. Make sure to check the condition of the air filter, replacing it if needed.

    3. Perform the Needed Tests

    Among the tests that can be performed include electrical tests of the MAP reference voltage of the MAP sensor, a ground test of the MAP sensor, as well as a live test for the boost pressure sensor.

    How to Solve the p0299 Code

    The action to solve the problem related to the p0299 code depends on the results of the diagnostics performed. It could be any of the following:

  • Repair of the boost pressure sensor connector and/or wires
  • Repair of the MAP sensor connector and/or wires
  • Repair of the exhaust pipe
  • Repair of the vacuum leaks
  • Replacement of the air filter
  • Replacement of fuel pump, inline filter, as well as other elements in the fuel system
  • Replacement of the turbocharger or supercharger

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