GMC Sierra 3500 HD loud engine noise with check engine light, clutch fan under repair on GMC Sierra 3500 HD

Some GMC Sierra 3500 HD owners report experiencing loud engine noises accompanied by a check engine light, particularly when the clutch fan is under repair. These issues may stem from insufficient or dirty oil, which can increase friction and cause knocking or tapping sounds. Additionally, worn or damaged drive belts, pulleys, or tensioners might produce squealing or screeching noises. A faulty clutch fan could also contribute to the loud engine noise. Furthermore, the check engine light may illuminate due to various factors, including a loose gas cap, spark plug issues, low oil pressure, O2 sensor malfunctions, catalytic converter problems, and more. This combination of symptoms indicates multiple underlying issues that require prompt diagnosis and resolution to prevent further damage and ensure the vehicle's performance.