Welcome to JustAnswer.com! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.
Is this the 5.2 or the 5.9 engine?
Ok- on these engine, as long as you are not hearing any "ticking" or "knocking" at idle, most commonly, this is a problem with the Oil Pressure Sender. It's fairly common that over time, the sender's internal resistance tends to wear out, and the sender has a hard time reading pressure at idle. Best place to start in the situation, is by replacing this sender. You will need a special tool - Oil Pressure Sender Socket - which is usually available at any local parts store.
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