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2018 Q50 Red Sport 400: Sudden Loss of Power and Check Engine Light (P0299)

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Heather Y. · rep 0 · May 22, 5:04 AM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 Red Sport 400

Hey everyone,

I'm having a really frustrating issue with my 2018 Infiniti Q50 Red Sport 400. Recently, while driving, I experienced a sudden and significant loss of power. The car felt sluggish, like the turbos weren't kicking in at all, and the Check Engine Light came on.

I managed to get it home and pulled the code, which came up as P0299 – Turbocharger/Supercharger Underboost. Has anyone else with the VR30DDTT engine experienced this? What was the fix?

It's really concerning, especially since this is supposed to be a performance engine. Any advice on where to start troubleshooting would be greatly appreciated before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:04 AM

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ClearTheCode admin answer:

The P0299 code indicates that the engine's computer has detected that the actual boost pressure is lower than the requested boost pressure. This is a common issue with turbocharged engines and can have several causes.

Common Causes & Diagnostics:

  1. Boost Leaks: This is the most frequent culprit. Check all intercooler piping, charge pipes, and vacuum lines for cracks, loose connections, or damaged clamps. A smoke test performed by a shop can quickly identify these.
  2. Wastegate Actuator Issues: The wastegate controls exhaust gas flow to the turbo. If its actuator (either vacuum or electronic) is faulty, stuck open, or has a damaged linkage, it won't build proper boost.
  3. Turbocharger Malfunction: While less common, a failing turbocharger (e.g., worn bearings, damaged compressor/turbine wheels) can lead to underboost. Listen for unusual whining or grinding noises.
  4. Diverter Valve/Bypass Valve Failure: These valves release excess boost pressure. If one is stuck open or leaking, boost will escape.
  5. MAP Sensor (Manifold Absolute Pressure) or MAF Sensor (Mass Air Flow) Issues: A faulty sensor can send incorrect readings to the ECU, leading it to miscalculate boost requirements or actual pressure.
  6. Catalytic Converter Restriction: A severely clogged catalytic converter can create excessive back pressure, hindering turbo performance.

When to See a Shop:

  • If you're not comfortable inspecting boost lines or don't have access to diagnostic tools (like a smoke machine).
  • If the issue persists after basic checks.
  • If you suspect internal turbo damage or wastegate actuator failure, as these often require specialized tools and expertise.
  • Continued driving with underboost can lead to reduced performance and potentially other engine issues if the ECU tries to compensate excessively.
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