The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2020 CX-9 2.5T Turbo Lag and Reduced Power - P0299 Code?

0

Chris P. · rep 0 · May 25, 3:33 AM · 1 replies · solved · Question

Vehicle: 2020 Mazda CX-9 Signature

Hello Mazda community, I'm having some performance issues with my 2020 Mazda CX-9 Signature, which has the 2.5L turbo engine. Lately, I've noticed a significant increase in turbo lag, especially when trying to accelerate from a stop or pass on the highway. It feels like the power just isn't there, and the engine struggles to build speed.

Sometimes, it even feels like it goes into a 'limp mode' where acceleration is severely limited, and the check engine light has come on a couple of times, though it sometimes clears itself. When it was on, I got a P0299 code, which I believe is for 'Turbocharger/Supercharger Underboost'.

The car has around 45,000 miles. I've been diligent with oil changes. Is this a known issue with the 2.5T engine in the CX-9? What should I be looking at?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:33 AM

0

ClearTheCode admin answer:

The P0299 code, "Turbocharger/Supercharger Underboost," on your 2020 Mazda CX-9's 2.5T engine is a clear indicator of an issue within the turbocharging system. This code means the engine's computer (PCM) has detected that the actual boost pressure is consistently lower than the commanded boost pressure, leading to reduced power and increased turbo lag.

Common Causes for P0299 (Underboost):

  1. Boost Leak (Charge Air System):

    • This is one of the most frequent causes. A leak in the intercooler piping, turbocharger hoses, or connections can allow boost pressure to escape. Even a small crack or loose clamp can significantly reduce boost. Inspect all visible hoses and connections for cracks, tears, or dislodgements.

  2. Wastegate Actuator/Valve Issues:

    • The wastegate controls the exhaust gas flow to the turbocharger turbine. If the wastegate is stuck open, or its actuator (which controls its movement) is faulty, exhaust gases bypass the turbine, preventing the turbo from building adequate boost.

  3. Turbocharger Failure:

    • While less common at 45,000 miles if maintenance is regular, a failing turbocharger itself (e.g., worn bearings, damaged turbine/compressor wheels) could result in insufficient boost. You might hear unusual whining or grinding noises if this is the case.

  4. Exhaust System Restriction:

    • A clogged catalytic converter or other exhaust restriction can impede exhaust flow, which in turn reduces the energy available to spin the turbo, leading to underboost.

  5. Boost Pressure Sensor (MAP Sensor) Fault:

    • A faulty Manifold Absolute Pressure (MAP) sensor might be providing incorrect readings to the PCM, causing it to misinterpret actual boost levels. However, this is less likely to cause actual power loss unless the PCM is reacting to the incorrect data.

When to See a Shop: Addressing a P0299 code promptly is important to restore your CX-9's performance and prevent potential long-term issues. You should take your vehicle to a Mazda dealership or a reputable independent mechanic specializing in turbo vehicles. They will typically:

  1. Perform a comprehensive diagnostic scan: To check for other related codes and live data.
  2. Conduct a boost leak test: This involves pressurizing the intake system to pinpoint any leaks.
  3. Inspect the turbocharger and wastegate: Visually and functionally check the components.
  4. Check exhaust back pressure: To rule out catalytic converter issues.
  5. Verify sensor readings: Ensure MAP and other relevant sensors are functioning correctly.

Driving with persistent underboost can stress other engine components, so timely repair is recommended.

Menu

Help & account