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2017 Malibu Premier 2.0T - P0299 Underboost and Loss of Power

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Ryan M. · rep 0 · May 22, 2:32 AM · 1 replies · solved · Question

Vehicle: 2017 Chevrolet Malibu Premier

I'm having a significant problem with my 2017 Chevrolet Malibu Premier, which has the 2.0L turbocharged engine. The check engine light recently came on, and when I scanned it, I got a P0299 code, which indicates an "Engine Underboost" condition. This makes sense because I've definitely noticed a significant loss of power, especially when I try to accelerate onto the highway or pass other vehicles.

The car feels sluggish and doesn't have that usual turbo 'kick.' It's like the turbo isn't really doing anything. I've got around 75,000 miles on the car. What are the most common causes for a P0299 code on this specific engine, and what should I check first?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:32 AM

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A P0299 code, indicating an 'Engine Underboost' condition, means your engine's turbocharger isn't producing the expected boost pressure. This directly translates to the loss of power you're experiencing. On the 2.0L turbocharged engine in your 2017 Malibu Premier, several components could be at fault.

Common Causes for P0299 (Underboost):

  • Vacuum Leaks/Boost Leaks: This is often the most common cause. Leaks in the intake system (intercooler hoses, charge pipes, vacuum lines) can prevent the turbo from building and holding pressure.
  • Wastegate Actuator Malfunction: The wastegate controls exhaust gas flow to the turbo. If its actuator (often vacuum or electronically controlled) is stuck open or failing, exhaust gases bypass the turbo, leading to low boost.
  • Diverter Valve/Bypass Valve Failure: This valve releases excess boost pressure when the throttle closes. If it's stuck open or leaking, boost pressure will escape.
  • Clogged Catalytic Converter: A severely restricted exhaust system can create back pressure, preventing the turbo from spooling up effectively.
  • Turbocharger Failure: While less common than leaks or actuator issues, the turbocharger itself can fail (e.g., worn bearings, damaged compressor/turbine wheels).
  • MAP/MAF Sensor Issues: Faulty Manifold Absolute Pressure (MAP) or Mass Air Flow (MAF) sensors can provide incorrect readings, causing the ECM to miscalculate boost requirements.

Troubleshooting Steps:

  1. Inspect Hoses and Connections: Visually inspect all turbocharger-related hoses, charge pipes, and vacuum lines for cracks, loose connections, or punctures. Pay close attention to the intercooler and its connections.
  2. Check Wastegate Actuator: With the engine off, locate the wastegate actuator and try to move the rod connecting it to the wastegate arm. It should have some resistance but move. If it's completely loose or stuck, it could be faulty.
  3. Listen for Hissing Sounds: With the engine running, listen carefully for any hissing sounds, especially under light acceleration, which could indicate a boost leak.
  4. Scan for Other Codes: Use your scanner to check for any other related codes (e.g., P0101 for MAF, P0106 for MAP) that might point to sensor issues.

When to See a Shop: If a thorough visual inspection doesn't reveal any obvious leaks or issues, or if you suspect a wastegate actuator, diverter valve, or turbocharger failure, it's best to consult a professional mechanic. They have specialized tools for boost leak testing, diagnosing wastegate operation, and can accurately determine if the turbocharger itself needs replacement. Driving with prolonged underboost can affect engine performance and potentially lead to other issues.

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