The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2019 CX-9 2.5T Turbo Lag and Reduced Power - P0299 Code

0

Sarah K. · rep 0 · May 22, 4:49 AM · 1 replies · solved · Question

Vehicle: 2019 Mazda CX-9 Signature

Hey everyone,

I've got a 2019 Mazda CX-9 Signature with the 2.5L turbo engine, and lately, I've been experiencing some noticeable turbo lag and a general feeling of reduced power. It's most apparent when I'm trying to accelerate quickly from a stop or when merging onto the highway. The car just doesn't feel as responsive as it used to.

Today, the check engine light came on, and when I scanned it, I got a P0299 code, which indicates 'Turbocharger/Supercharger Underboost'. This definitely aligns with what I'm feeling. Has anyone else with a 2.5T CX-9 had this issue? What was the fix?

I'm hoping it's not a major turbo replacement, as that sounds expensive. Any insights or common solutions would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:49 AM

0

ClearTheCode admin answer:

The P0299 code (Turbocharger/Supercharger Underboost) on your 2019 Mazda CX-9 2.5T is a clear indicator that your engine isn't receiving the expected boost pressure. This directly explains the turbo lag and reduced power you're experiencing. Here are the common causes and diagnostic steps:

  1. Inspect for Leaks in the Intake System:

    • Charge Air Cooler (Intercooler) Hoses: Check all hoses connecting to and from the turbocharger and intercooler for cracks, loose clamps, or punctures. Even small leaks can cause significant boost loss.
    • Intake Manifold Gasket: A leaking intake manifold gasket can also lead to boost loss.

  2. Wastegate Actuator/Valve Issues:

    • Stuck Wastegate: The wastegate controls the amount of exhaust gas that bypasses the turbocharger turbine. If it's stuck open or not closing properly, boost pressure won't build up. The actuator arm can sometimes become disconnected or faulty.
    • Wastegate Solenoid: The solenoid controls the wastegate actuator. A faulty solenoid can prevent proper wastegate operation.

  3. Boost Pressure Sensor (MAP Sensor):

    • Faulty Sensor: A malfunctioning Manifold Absolute Pressure (MAP) sensor can send incorrect boost readings to the engine control unit (ECU), causing it to limit boost or misinterpret actual pressure.

  4. Turbocharger Health:

    • Internal Wear: While less common on newer vehicles, internal wear or damage to the turbocharger itself (e.g., worn bearings, damaged turbine/compressor wheels) can lead to underboost. This is usually accompanied by whining noises or excessive smoke.

  5. When to See a Shop:

    • Given the complexity of turbo systems, professional diagnosis is highly recommended, especially with a P0299 code.
    • A mechanic can perform a smoke test to find leaks, check wastegate operation with a vacuum pump, and monitor boost pressure readings with a diagnostic scanner.
    • Ignoring underboost can lead to poor performance, reduced fuel economy, and potentially further engine issues.
Menu

Help & account