What could be the sound ? There are no engine codes.
I replaced my alternator. After replacing the alternator i still hear a sound> on 2006 Nissan Altima
Many newer design alternators have clutches in them and it is normal to hear a little noise when first shutting off engine and alternator is coasting down, otherwise you may have something else making a similar noise or have a defective replacement alternator. Call Roy at 757-456-0722 if you would like a free loaner vehicle while we check and correct it for you.