Tech Tip: Common Diesel Engine Noises
Customers may comment on various noises they hear and ask about what’s causing them. The noises are described below and may be heard when the engine is running or after it’s turned off. Advise the customer that these noises are a normal function and operating condition of the L5P diesel engine.

Vehicles Involved: 2017–2020 GMC Sierra and Chevrolet Silverado models with the 6.6L V8 Duramax Diesel (L5P) engine

This only occurs during deceleration and is usually heard (but not limited to) coming from the passenger side of the vehicle. The noise stems from the fuel injectors firing — one injector per deceleration and not always the same injector.

Some noises may come from under the hood after the engine has been turned off. You may notice that they are the same noises almost every time. These sounds are coming from the turbocharger and/or intake airflow valve, which is a throttle plate actuator that’s used to achieve high exhaust gas recirculation rates. The parts cycle through their normal operating ranges after the engine is turned off.

This noise is present in all diesel engines produced during the last 20 years, and has no impact on engine reliability and durability. The noise occurs at idle and may seem louder when standing just behind the front wheel on the driver’s side. It also may be more noticeable during the first 20 percent of engine oil life.

A ticking sound may be heard coming from under the vehicle at low vehicle speeds — especially when next to a building, as when approaching or leaving a drive thru window. This noise also may be heard at idle on 2019 and 2020 vehicles.

Remember, these noises are a normal function and operating condition of the L5P diesel engine.

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