What does the P0299 OBD-II code mean?

The P0299 code is a generic powertrain diagnostic code applicable to vehicles equipped with a turbocharger or supercharger. When the OBD-II P0299 trouble code triggers, it indicates an underboost condition with either the Turbo or Supercharger “A”, giving excessively low output. The vehicle’s ECU sets the code when it detects this low boost.

How serious is the P0299 code?

The P0299 diagnostic code is considered severe and should be addressed as soon as possible. It can indicate serious mechanical failures and, if accompanied by any mechanical noise and/or driveability issues, should be investigated and repaired quickly. For example, if the turbocharger fails and the car continues to be driven, it may damage engine components. In a nutshell, even a minor issue with a supercharger or turbocharger can turn into a serious problem which means costly repairs if you don’t resolve it quickly.

What are the common symptoms of trouble code P0299?

You can expect the following symptoms when a P0299 code is triggered:

  • Illuminated Check Engine light
  • Very little difference (or none) in acceleration (when supercharger/turbocharger is engaged)
  • General lack of acceleration/engine power
  • Mechanical noise if failing turbo/supercharger or the sound cuts in and out

What are the causes of a P0299 diagnostic code?

There are a limited number of reasons for a P0299 diagnostic code triggering:

  • Defective supercharger or turbo
  • Low engine oil pressure
  • Emission Gas Recycler (EGR) defect
  • Air or air intake leak or restriction
  • Boost pressure sensor is faulty

How to diagnose a P0299 OBD-II code?

Using an OBD-II scanner or booking a diagnostic check with a trusted mechanic or garage is the quickest way to diagnose an OBD-II fault code. Following the diagnostic steps fully and correctly is essential for accurate diagnosis:

  • See if there are any technical service bulletins available for your vehicle’s model and make to check if there is a known problem for your car that can help resolve the issue.
  • Use an OBD-II scanner to scan the vehicle for any codes present and note all freeze-frame data, which will contain the conditions the car was under when the code was set.
  • Reset the fault codes and take the car for a test drive to check if the code returns.
  • If the code persists, visually inspect the turbocharger/supercharger system, intake system, EGR system, and any other associated systems.
  • Check for proper boost pressure readings.
  • Inspect all mechanical systems, including the supercharger or turbo, oil pressure and the intake system for blockages or leaks.

How to fix a P0299 OBD-II trouble code?

It is prudent to test drive the vehicle after each action is performed to see if the fault code clears. If the P0299 code returns, move on to the next repair. The most common repairs are:

  • Confirm the fault code with an OBD-II scanner, and then reset. Follow this up with a test drive of the car to see if the trouble code clears. If it returns:
  • Repair or replace any loose or damaged parts of the intake air system which could be causing a pressure leak (common)
  • Replace air filter
  • Repair low engine oil pressure issue
  • Repair boost pressure sensor wiring and/or connectors.
  • Replace the boost pressure sensor
  • Replace EGR