Q: Whining noise before starting-key in the ON position but not turning over the engine. 1999 Chevrolet Silverado 1500

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I noticed the noise because there's that brief moment before you turn the key, so I just put the key in the on position to listen. It makes whining or howling noise for about 3 seconds. I listened to the noise both under the car and inside the engine compartment; it sounds like it's coming from the engine compartment. I took the top cover off the engine but I still can't source it. Starter seems to be fine; it's new and the noise was there before and after the new starter.

My car has 230000 miles.
My car has an automatic transmission.

Hello - your truck has a secondary air injection pump, which is powered by an electric motor. It is located under the hood, and is power up in the "Run" ignition switch position. I suspect what you are hearing is this pump spinning up. If the noise seems louder than reason would suggest, perhaps the bearings are worn out, and a replacement air pump is in your future. For further diagnosis, I recommend a noise inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

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