Loud Whining Noise & Lean Codes on a 2021 GMC Sierra 1500 🔧 | AG Auto Tech

Описание: Customer complaint: loud whining noise that gets louder with speed on this 2021 GMC Sierra 1500. Check engine light on with codes P0171, P0174 (lean both banks), P0300 (random misfire), and U0184.

These 5.3/3.6 GM engines are known for vacuum leaks — often the valve cover PCV system or intake manifold gaskets.

Quick tip: always verify with a smoke test before replacing parts!

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